Visionary ( episode ) After receiving a minor dose of radiation poisoning , O ' Brien inexplicably begins experiencing a series of jumps into the near future . Meanwhile , a Romulan delegation arrives on the station , expecting an intelligence report on the Dominion . Summary . Teaser . Dr . Bashir is tending to Chief O ' Brien in the Ops pit . When O ' Brien asks what happened , Commander Sisko tells him that one of the plasma conduit s blew out while he was attempting to re - route a phase inducer . Bashir tells him that he has a mild case of radiation poisoning , before injecting him with a dose of hyronalin to counter the effects . The doctor recommends O ' Brien be placed on light duty for the next few days . Sisko agrees . Before they can discuss the matter further , Major Kira interrupts with news that a Romulan delegation has arrived and is requesting permission to dock . Sisko allows them to dock at bay 12 ; he and Kira will meet them there . Before heading out , the Commander gives O ' Brien one word of advice . " " Light means light , " " he says . Sisko doesn ' t want O ' Brien spending the night crawling through Jefferies tube s looking for power surges . The Chief jokingly replies , " " You won ' t get any arguments today , Commander . " " On the Promenade , Kira and Sisko are on their way to meet the Romulan delegation when a drunken Klingon staggers out of Quark ' s , assisted by two Bajoran security guards . Constable Odo explains that a Klingon freighter had to dock with the station and , due to a computer error , will not be able to depart until it is repaired , which will take at least two more days . Sisko takes Odo aside and asks him to keep a close eye on the Klingons , as the commander doesn ' t want them to get in the way of the Romulans . Odo acknowledges Sisko ' s request and the drunken Klingon is taken to a holding cell . Kira and Sisko continue to the docking port , where two Starfleet security guards are waiting . The circular doors are wheeled back and a Romulan named Ruwon steps out , followed closely by his aide , Karina , and two guards . Sisko offers them accommodation after their long trip but all Ruwon is interested in are intelligence reports on the Dominion . The commander exchanges a brief glance with Kira , before escorting their guests to the wardroom . In his bar , Quark is hanging up a dartboard for O ' Brien , but he is skeptical it will bring him any profit . The chief , in his confidence , notes that " " darts and bars go together like bacon and egg s " " to which Quark reminds him that people actually order bacon and eggs , and no - one has yet asked to see a dartboard . In an attempt to convince , O ' Brien hands Quark some darts and challenges him to hit the bulls - eye . Quark , unaware of how to play the game , throws them all at once , hitting Morn non - fatally in the process . The Ferengi points out how dangerous the game is ; after all , if one of his customers was injured , he could be held liable . But the chief doesn ' t give in and picks up a dart , intent on showing Quark how the game is properly played . As he aims for the board , there is a bright flash of light and he is transported to the upper level of the Promenade . But something isn ' t quite right . O ' Brien looks across the way and sees himself , arguing with Quark about the damage the Klingons are doing to two of his holosuite s . A confused look comes across his face as the other O ' Brien tells Quark to keep the Klingons out of the holosuites from now on . Finishing his conversation , he turns away , and the two lock eyes , both incredibly confused by what is happening . But before they can say anything , the original O ' Brien is back in Quark ' s . His dart hits the bulls - eye and he falls to the floor , disoriented . Act One . In the infirmary , Doctor Bashir explains that the chief ' s earlier collapse was due to a sudden decrease in his serum calcium levels , a common side effect of the radiation poisoning , and gives him a dose of asinolyathin for the pain . The doctor continues to explain that his " vision " was also likely a mild side - effect , though the Chief isn ' t fully convinced . He explains it to Bashir , who jokingly mocks him , saying he has a " sadly deficient fantasy life " . On that note , O ' Brien sarcastically " thanks " the doctor for his help and leaves . In the wardroom , Ruwon proclaims that the Dominion is the greatest threat the Alpha Quadrant has seen in the last century and wants to know exactly what Sisko and his crew have obtained through use of their cloaking device on the . When the commander admits they know very little , Karina responds , asking about Odo , incorrectly referring to him as a Founder . She believes he can tell them all they need to know about the Dominion , though Major Kira soon corrects her , informing her that Odo may be a Changeling but he is not a Founder and wants nothing to do with them . The commander backs her up by telling them it is the truth , " " whether they chose to believe it or not " " . Ruwon reminds Sisko that they agreed to install the cloaking device in exchange for information on the Dominion , but they have received very little so far . He goes on to demand every piece of information Starfleet has on them no matter how insignificant , including any classified reports made to Starfleet Command . Sisko says he will have to clear it with his superiors first . On the upper level of the Promenade , Quark is complaining to O ' Brien about the damage the Klingons have caused to the holosuites . In the middle of his sentence , O ' Brien stops and , remembering his previous vision , looks across the way to where he was standing before . Another O ' Brien is standing there , watching them . This time , Quark sees him too and observes that O ' Brien has bigger problems than his holosuites . A few seconds later , the other O ' Brien disappears . In Sisko ' s office , Jadzia Dax reports that she did detect a minor temporal disturbance in Quark ' s , and another later on the Promenade , round about the same time O ' Brien had his visions . It soon becomes apparent that O ' Brien did travel to the future and then back again , to the same moment he left . Dax theorizes that the ion izing radiation he was exposed to earlier may have something to do with it and wants to examine Doctor Bashir ' s medical scans . Before she can explain further , the chief flashes back to Quark ' s in the middle of a bar fight and sees himself fighting with a Klingon . After finishing off a Romulan , another Klingon takes out his " d ' k tahg " and heads towards him . O ' Brien quickly grabs the Klingon ' s arm , knocking the dagger away and throwing him to the floor . Just as he avoids a bar stool being thrown at him , he flashes back to the Commander ' s office , where he again collapses to the floor . Dax and Sisko quickly rush to his aid , but he doesn ' t respond ; he is unconscious . Act Two . Back in the infirmary , Bashir has run a micro - cellular scan and has detected damage to O ' Brien ' s cerebrospinal nerve cell s , which he thinks has been caused by the timeshifting . The doctor explains that while he can repair the current damage , the effect is cumulative and that there may come a time , if the timeshifting continues , when he can no longer repair the damage , and O ' Brien could die . Sisko comforts him , saying Dax is using every scanner on the station to hunt for any temporal abnormalities , which is of some relief to O ' Brien . " " If anyone can find the cause of the timeshifts , it ' s Dax " " , he says with a relaxed smile . The commander goes on to ask him if he was aware how far ahead the timeshifts are taking him , in case it affects the meeting with the Romulans , but he doesn ' t know . Sisko decides to ask Odo to increase security around Quark ' s just in case . At that moment , Major Kira walks in and , after asking how O ' Brien is , she walks Commander Sisko onto the Promenade . As they pass a Bajoran stall , she explains that the Romulans want to debrief everyone who was on the " Defiant " when it was captured by the Founders and unrestricted access to the ship and all personal logs . Sisko immediately rejects access to personal logs , but decides to permit them limited access to the ship and debriefings of crew . He explains to Kira how the Romulans are completely dependent on them for information to which a frustrated Kira suggests they send their own ships through the wormhole . He continues to explain how the Romulans generally prefer to sit back and pull the strings from a distance if they can , and though Kira replies she is one puppet who doesn ' t like her strings pulled , she accepts his orders . As they part ways , Sisko reminds her to be diplomatic , to which she replies " " I ' m always diplomatic ! " " . In the wardroom , Kira yells at the Romulans for insinuating she abandoned the " Defiant " prematurely during the battle with the Jem ' Hadar but they only see her emotional outburst as evidence that they are correct . Relaxing a little , she continues to explain how she was trapped in a hand - to - hand fight below decks and was knocked unconscious , before Odo put her on the shuttle . She says she only came to after they had left the ship and there was nothing they could have done . Ruwon begins to question why Odo didn ' t help any of the other crew but Kira defends him , insisting they were blocked in . Karina then asks her why she was in Odo ' s quarters before the attack and rather keenly suspects the Odo might be harboring feelings for Kira , which pushes Kira further over the edge . She puts an abrupt end to their questioning saying they can rip the cloaking device from the " Defiant " and advises them not to ask Odo the same questions or they may just find themselves on the other side of the bulkhead , floating home . Ruwom and Karina share a nervous glance as Kira storms out of the room , pushing the guards to one side . In Quark ' s , Bashir has just beaten O ' Brien in the tenth game of darts in a row . He tells the chief that because he has told them what happened he has changed the future , and with the increased security and Quark ' s promise not to let the Klingons in , the fight won ' t happen , though O ' Brien isn ' t entirely convinced . Just then , three Klingons make their way down from the holosuites . The chief grabs Quark by his arm and demands an explanation as to why they are in the bar . Pulling out a bar of latinum , he replies that the Klingons weren ' t in the bar , they were in the holosuites , and besides , they are paying him triple to use them . The three Klingons walk over to the two Romulans sat down and call them " " filthy petaQ " " . Another suggests they " " show them the way out " " . Not ones to take insults , the two Romulans stand and confront their aggressors . In the security office , Kira is telling Odo what Ruwon said about them , which makes Odo feel slightly uncomfortable given that he does have feelings for her . They are suddenly interrupted by a call from Quark ; a fight has broken out in the bar . O ' Brien gets into a fist fight with a Klingon , knocking him to the floor . He then sees his younger self , who attacks another Klingon wieldying a " d ' k ' tagh " thereby fulfilling his second vision . As he warns his past self about the flying bar stool , Odo rushes in and breaks up the fight . But before O ' Brien has a chance to recover , he is again flung into another future . This time , he appears in a corridor in the habitat ring where he sees his future self opening a panel . He calls out to him but before he can do anything a sharp bolt of energy is fired out from the panel , knocking his future self to the ground . The chief rushes to see if he ' s alright , but after feeling his pulse , he realizes he is dead . O ' Brien awakens in the infirmary where he was taken after the fight . Bashir tells him everything is OK and he ' s going to be alright , but O ' Brien knows otherwise . " " No , I ' m not " " he says , " " In a few hours I ' m going to be dead ! " " . Act Three . Sisko , O ' Brien , and Odo are in the corridor where the accident happened . The chief believes it was some sort of phaser or high - energy laser that killed his future self but a scan of the bulkhead reveals nothing . Odo carefully opens the panel but again there is nothing by the computer display inside . They theorize that the perpetrator has yet to plant the device but he will do so in the next few hours . Odo suggests placing a surveillance device in the corridor so they can observe if anyone does indeed try and tamper with the panel , at which point they are interrupted by Dax over the comm system . She wants Sisko and O ' Brien to head up to Ops ; she says she has found a clue as to the chief ' s timeshifting . Up in Ops , Dax explained she tried several scans of the surrounding space but got nothing until she ran a scan on the lower subspace bandwidths with turned up some curious tetryon emissions . O ' Brien remarks he hasn ' t seen emissions like that outside of a neutron star . Dax , however , suggests the presence of a quantum singularity , the only strange thing is that it isn ' t affecting the gravimetric field signature of the station as it should . Sisko , assuming that a quantum singularity is responsible , turns to Bashir and asks how its effects can be combated . Bashir theorizes that the singularity is attracted to the delta series radioisotope s in O ' Brien ' s body , effectively pulling him along like a magnet . And if that ' s the case , he may have a cure for it , but it ' s going to take time . He warns the Chief that he could experience one or two more time jumps before the process has been completed . O ' Brien wants to get started right away , and so heads down to the infirmary with Bashir . Meanwhile , Sisko orders Dax to continue to pinpoint the singularity in an effort to get rid of it . Just then , Major Kira enters Ops and informs the commander she had to move the Romulans to alternative quarters as the replicator s were malfunctioning . It just so happens that the quarters she has moved them to are on level 2 , section 47 , directly adjacent to the area where the future O ' Brien was killed . Kira suggests moving them to a different room , but Sisko objects so as not to alert those responsible . Instead , he tells her to inform Odo and let the scenario play out before they make any further moves . A short while later , Sisko is summoned to Odo ' s office where he informs him that someone has planted a class 3 surveillance device in the bulkhead , though he doesn ' t know who as they used a low energy transporter to put it there . He goes on to say that although they cannot trace the transporter signal , he believes it originated from the station as there were no ships in range at the time . The Klingons are the prime suspects but Odo also intends to investigate the Bajorans , Quark , and the visiting Terellian s just to make sure . In Quark ' s , Bashir and O ' Brien are waiting out the time he has until his death in the other future when Quark arrives with the drinks they ordered . Being his usual self , he also asks O ' Brien to keep an eye out for the numbers on the dabo wheel next time he jumps into the future . O ' Brien doesn ' t pay any attention to him and suggests he and Bashir leave . As they exit the upper level , O ' Brien is again flung into the future , this time he is in the infirmary . He notices a body on one of the biobed s , covered in a white sheet . He slowly walks towards it and lifts the top to reveal his own corpse . Act Four . O ' Brien covers up his dead body lying on the biobed when Bashir walks round the corner . He had been expecting him and has some important news for the chief to pass onto Bashir ' s past self . The radiation had damaged the basilar arteries in O ' Brien ' s brain stem which hadn ' t shown up on any scans and was only picked up in the autopsy . Bashir instructs him to tell his former self to run a basilar arterial scan so he can detect and repair the damage in time . O ' Brien begins to argue with Bashir about his inability to save him , but he flashes back to the upper level of the Promenade . O ' Brien falls to the floor and Bashir summons a nurse and an emergency medkit there immediately . In the habitat ring , Odo explains to Sisko that he was finally able to trace back the source of the transporter beam to some empty quarters . Sisko speculates that they brought in a portable transporter but Odo quickly discounts it as the technology is too bulky to be dragging around the halls . Sisko nods in agreement as Odo continues to explain how they modified the replicator , turning it into a mini - transporter by realigning the matter energy conversion matrix ; a very sophisticated and professional job . Reaching into the replicator circuitry , Odo pulls out a device which he says is manufactured on Davlos III , a planet on the Klingon border and which does ninety percent of its trade with the Klingon Empire . Sisko doesn ' t think it is enough to hold the Klingons and Odo agrees but there ' s more . A friend at Starfleet Intelligence that used to be assigned to the Federation embassy on Qo ' noS put him in contact with an old Klingon operative who provided him with information showing the three Klingons currently on the station are part of a covert strike force , reporting directly to the High Council . They now have enough to hold the Klingons for questioning , questioning that Odo feels can continue until after the Romulans have left the station . Sisko agrees though tells Odo to be careful , to which he replies , " " There is no careful way to question a Klingon " . " O ' Brien is back in the infirmary where Bashir is scanning him . He wakes up and tells Bashir he needs to run the basilar arterial scan or he ' ll die within a few hours . " " Well , who am I to argue with me " ? " , Bashir jokes . Meanwhile , Odo has arrested the three Klingon operatives : Bo ' rak , Atul and Morka and has placed them in a holding cell for the time being . He accuses them of being spies and saboteurs , to which they simply reply with threats of vengeance . Odo tries a threat of his own by telling them if they help him he will forgo telling the Klingon Intelligence service that they have been captured . He says from what he hears they frown on operatives who fail their missions . The Klingons look at each other thinking about his offer . Back in Ops , Bashir informs Sisko that he has eliminated almost all of the radioisotopes from O ' Brien ' s system and the last treatment is in a couple more hours , after which there should be no more timeshifting . Dax also reports that the quantum singularity is orbit ing the station in a roughly elliptical pattern . O ' Brien continues by saying the anomaly radiates temporal energy at certain points in its orbit which seems to be causing his timeshifts . At that very moment , he shifts again . There are lots of people scrambling into a runabout . His future self is at the helm and initiates an emergency escape protocol , disengaging the docking clamp s and immediately engaging full impulse . All three of the station ' s runabouts hastily escape the vicinity as explosions cascade across the habitat ring . The future O ' Brien explains he was sleeping when an explosion rocked the station and was on his way to Ops when the evacuation alarm sounded , so got as many people as he could to the runabout before leaving . He tells O ' Brien that doesn ' t know what happened or if the other senior staff made it off the station , and urges him to find out what happened and prevent it . As the runabout flies away , the explosions engulf the station , destroying it . At that point , the wormhole opens only to suddenly collapse an instant later . O ' Brien watches the events in horror before he shifts . Back in Ops , Sisko asks the chief what ' s wrong . " " We ' ve got a new problem , sir " . " he replies . Act Five . Sisko questions O ' Brien on his latest timeshift , asking for any clue of how the station may be destroyed . O ' Brien says he noticed some explosions along the habitat ring but it all happened so fast that he couldn ' t get a clear sense of exactly what was going on . The commander orders a silent preparation for evacuation should it need to come to that , but he doesn ' t want to do anything that would alarm their enemy into attacking sooner . He also orders Dax to do a complete systems check on anything that could potentially cause this type of disaster . The chief also has an idea . If they could cause him to travel into the future on purpose , this time only by two or three hours , he may be able to find out what the threat is and stop it happening in their timeline . Bashir notes the problem with the plan ; in order to do this , O ' Brien ' s body would need to be flooded with delta series radioisotopes and prolonged exposure would kill him . But the chief knows the risks and is willing to do it if it means saving everyone on DS9 . After thinking on it for a few seconds , Sisko approves his plan and they get to work . In the infirmary , Bashir instructs O ' Brien on a rectangular device designed to inject him with a two rad dose of delta isotopes . He explains to him that the device is already calibrated for the return trip so all he has to do it press it again to return to the present . Bashir warns him that he cannot wait too long or his body will fail due to severe radiation poisoning . On another note , O ' Brien mentions a message to Keiko that he has left in his quarters . He wants Bashir to deliver it should the plan fail . Bashir understands . Upon activating the device , O ' Brien is transported to his quarters where the future O ' Brien is asleep . He manages to wake him and explains the situation . The two of them quickly head for Ops and on arrival a Romulan warbird decloaks and opens fire on the station , taking out the shield generator s in the first shots . Kira orders return fire but it is no use , the Romulans have hit the power core . The future O ' Brien realizes the orbiting quantum singularity was the power source of the Romulan ship and tells O ' Brien to go back and stop it . But he can ' t . The radiation poisoning has taken its toll on his body and he would die if he did , and would then be unable to warn the crew . Instead he takes off the device and hands it to future O ' Brien , convincing him to go back in his place . The new O ' Brien wakes up in the infirmary next to Doctor Bashir , who asks how it went . After confirming it worked , O ' Brien immediately contacts Sisko in Ops , who raises the station ' s shields and readies weapons . Bashir quickly realizes that this O ' Brien is different ; he doesn ' t have nearly as many delta isotopes in his body and his metabolic readings are completely different . In the wardroom , the Romulans are interviewing Quark , when Sisko , Kira and Odo barge in . The commander tells him to leave before revealing what he knows to Ruwon and Karina . He tells Ruwon how he remembered what he said about the Dominion being the greatest threat to the Alpha Quadrant for a century and that if he truly believed that he would want to close the wormhole for good . Kira finishes by saying that the Federation and Bajor wouldn ' t just stand by and watch them do it so they would have to destroy the station as well and make it look like an accident . The two Romulans deny the allegations calling it a mere " theory " . But Sisko responds by informing them he has about fifty photon torpedo es locked onto their ship . He then asks Odo to escort their " guests " to the nearest transporter room . In Quark ' s , over darts , O ' Brien tells Bashir how weird it is to be living in the past , that it is like living the other O ' Brien ' s life . Bashir says that he ' s the same O ' Brien , just with a few extra memories . As he leaves , he whispers in Quark ' s lobe , " " dabo " . " Quark doesn ' t understand what O ' Brien means until a small crowd at the wheel yells , " " Dabo ! " " Quark then yells for O ' Brien to come back , who simply walks away , laughing . Memorable quotes . " " Well , you do have one problem . . . if all you can hallucinate about is Quark ' s maintenance problems , you do have a sadly deficient fantasy life . " " " " Major , when you ' re with the Romulans , try to be diplomatic . " " " " I ' m always diplomatic ! " " [ screen cut ] " " That is the most ridiculous thing I ever heard and I resent the implication ! " " " " But don ' t worry – I plan to investigate the Klingons , the Bajorans , Quark , the visiting Terrelians . . . " " " " You think Quark had something to do with this ? " " " " I always investigate Quark . " " " " Why didn ' t you just say so ? " " " " Well sometimes I have to remind you just how good I am . " " " " I think we have enough evidence to at least hold the Klingons for questioning , don ' t you ? " " " " Absolutely . And I think I can question them until the Romulan delegation leaves the station . " " " " Just be careful . " " " " Commander , there is no careful way to question a Klingon . " " " " I think you ' re lying , Quark . " " " " About which part ? " " " " All of it . " " " " Well , at least I am consistent . " " " " Who told you that ? " " " " You did . In the future . " " " " Oh . Well , who am I to argue with me ? " " " " I hate temporal mechanics . " " Links and references . References . Alpha Quadrant ; artificial quantum singularity ; asinolyathin ; autopsy ; Bajoran s ; Bajoran wormhole ; basilar artery ; basilar arterial scan ; brain stem ; burp ; cerebrospinal nerve cell ; cloaking device ; constable ; dabo table ; darts ; ; Davlos III ; ; delta - series radioisotope ; Dominion ; Dominion cold war ; embassy ; emergency medkit ; emergency power ; Federation ; fortune teller ; Founder s ; Gamma Quadrant ; Gowron ; gravimetric field ; habitat ring ; high - energy laser ; holosuite ; hyronalin ; Jefferies tube ; Jem ' Hadar ; kilometer ; Klingon ; Klingon Empire ; Klingon freighter ; Klingon High Council ; Klingon Intelligence ; Klingonese ; laser ; lie ; Markalian s ; matter - energy conversion matrix ; medical scan ; microcellular scan ; muscle spasm ; neutron star ; ; personal log ; phase inducer ; phaser ; portable transporter ; power coupling ; Promenade ; Qo ' noS ; quantum singularity ; Quark ' s ; rad ; radiation poisoning ; replicator ; Romulan s ; Romulus ; runabout ; shield generator ; Starfleet ; Starfleet Command ; Starfleet Intelligence ; subspace bandwidth ; surveillance device ; temporal energy ; temporal frequency ; temporal mechanics ; Terrelian s ; tetryon ; tricorder