Cathexis ( episode ) " Voyager " attempts to investigate the force that made Chakotay brain - dead , while an unknown entity keeps turning them back . Summary . Teaser . Captain Kathryn Janeway is taking part in a holonovel set in " ancient England " when she is called to the bridge by Harry Kim , who announces that the shuttle Chakotay and Tuvok are in has appeared on long range sensor s but has not answered hail s . The shuttle has taken damage with multiple hull fracture s and life sign s are faint ; Janeway orders the two to be beamed to sickbay when they are within range . In sickbay , The Doctor says that both Chakotay and Tuvok have taken blows to the head by an energy discharge of some kind . Tuvok incurs a concussion which is treatable , but Chakotay had been drained of all bio - neural energy from the brain and is in some form of coma . Although The Doctor can keep the commander on life support , he declares that there is not much he can do because he is brain dead . Act One . Tuvok explains what happened on the shuttle when they were attacked . After conducting a trade mission with the Ilidarian s , they had an unexpected encounter with a dark matter nebula , where an unknown vessel attacked them . He says that he was barely able to set the shuttle on autopilot to return to " Voyager " . Janeway decides to return to the nebula to investigate and find the ship that attacked them . In sickbay , B ' Elanna Torres uses a medicine wheel to aid Chakotay through a healing ritual he had previously taught her . Chakotay has always been a very spiritual man and she believes the wheel and its grander meaning might be Chakotay ' s only chance now . She explains that when a person is sleeping or on a vision quest , it is said that he is walking the wheel and the placement of each stone acts as a signpost to help point the way back home . Kes , having a strange feeling that someone else is in her quarters , goes to the mess hall to tell Neelix . Janeway notes the nebula is emitting intense electromagnetic radiation that is preventing the sensors from detecting anything . Attempting to change the sensors to utilize a multiphasic bandwidth to penetrate the radiation , she suddenly " loses " the nebula and discovers that " Voyager " has been put on a course away from it . They wonder who turned the ship around and find that the course change came from Tom Paris ' station at the conn . Paris denies doing anything and faults the console . The captain orders Kim to transfer helm control to ops and resume their previous course while she orders Paris to helm control to see if there is something wrong with the ship ' s systems . After the ship shudders , however , Janeway discovers it has changed course once again , and orders Kim to get the ship back on course – but this time the helm doesn ' t respond because it has been locked out . Act Two . Tuvok investigates the source of the lockout and finds it came from navigational control on Deck 12 . Paris returns to report he checked every ODN junction in helm control and found no problem . Tuvok establishes helm control once again and resumes course . Janeway asks Torres if anyone is currently at the navigational controls . Torres says that she in fact saw Paris there only a few moments ago . Paris is surprised and once again denies having been there and everyone is dumbfounded at the fact that he was at the navigational controls in both instances when the ship changed course . However , Janeway gives him the benefit of the doubt , ordering him to report to sickbay to check his memory . The Doctor runs some scans on Paris and reports to Tuvok that nothing out of the ordinary has been found . Tuvok , however , reports that his scans of the navigational controls reveal traces of Tom Paris ' DNA . As the ship continues on course to the nebula , Tuvok indicates that he believes he has found the ion trail of the ship that attacked the shuttle leading back into the nebula . Noting the highly erratic flight path , Janeway suggests that the planetoid s the trail bends around could be generating gravitational effects that cause currents within the nebula . She hypothesizes the route the unknown vessel took may be the only safe way through the currents . Before Janeway can order the ship to follow the ion trail , however , there is a massive energy drain throughout the ship . The warp core begins to shut down , causing " Voyager " to drop to impulse power . After getting no response from engineering , the captain and Tuvok head down to investigate . Janeway finds Torres at the warp core controls , where Torres has initiated an emergency warp core shutdown leaving the ship unable to regain warp drive for at least two hours . Janeway explains to a baffled Torres that the engineer has just crashed the main computer , locked out the bridge , and stopped the ship cold , for which Torres has no explanation . She cannot recall having done any of that . Janeway finally realizes that there is something very odd going on here , as Torres – after Paris – is the second person not remembering having input commands into the ship . In sickbay , The Doctor shows the captain the results of his scans of Torres ' and Paris ' memory engram s . The results show a different memory pattern during the exact time Paris allegedly changed the ship ' s course and lost recollection , and again when he was tampering in navigational control . Further , the same disruption has been found in Torres when she shut down the warp core . The Doctor explains further that the signature is bio - neural and he believes it to be another brain wave that has been superimposed onto theirs , believing an unknown alien entity having temporarily taken control of their bodies . Janeway observes that the alien seems intent to prevent " Voyager " from getting to the nebula , and that it possesses the ability to take control of anyone at any time , except for The Doctor . She decides it would be best to transfer all command codes to The Doctor for fear of the alien taking over any of the senior staff using authorization code , " Janeway 841 - Alpha - 65 " . Later , Kes catches up with Tuvok in the corridor , and reports that she has been sensing some strange things on the ship . Tuvok offers to mind meld with Kes to see if they can find the entity with Kes ' telepathic abilities . But the two get no further than the turbolift , where Kim and Lieutenant Durst discover them unconscious . Act Three . In a darkened conference room , Tuvok explains that an energy discharge came out of the bulkhead and filled the turbolift , knocking them both unconscious , just as it had happened on the shuttle . Torres reports that they picked up no unusual readings from the internal sensors . Paris suggests the use of a magneton scanner in hopes that a more detailed scan may reveal the source of the discharge . Torres , however , proposes to use the magneton scanner on the entire ship all at once in order to detect the exact location of the entity . She asks Kim for his thoughts on the matter , when she notices that he is motionless and staring out into space . Nervous that he might be possessed by the alien , Tuvok pulls his phaser out , while Torres conducts a personal scan via tricorder . Kim finally snaps out of his thoughts , explaining that he was merely pondering about a possible way to solve this and that he is not possessed . Janeway , disturbed by what just happened and the increasing paranoia , orders preparations for the magneton scan . While scanning Kes , The Doctor finds himself in the company of Neelix . Neelix recounts the strange behavior of every crewman on board , noting that Ensign Parsons ordered his pejuta cold instead of hot . After a brief debate on who really is paranoid , The Doctor explains that Kes hasn ' t suffered any permanent neurological trauma and that he will notify Neelix when she is revived . After Neelix leaves , Tuvok enters to modify the sensor array in sickbay for the magneton scan . The Doctor tells Tuvok that Kes ' injuries don ' t match Chakotay ' s , pointing out contusions on her neck and shoulder that are consistent with something similar to a physical struggle . Tuvok informs the Captain that the magneton scan will be ready in two hours , and that its use will cause dizziness and disorientation throughout the ship . He further reports that The Doctor has found evidence that Kes ' injuries were a result of a physical assault . Janeway suggests that because Tuvok wasn ' t assaulted , it is possible he injured Kes while under the influence of the entity . She calls sickbay to notify The Doctor to conduct a scan on the security chief , only to get no response . Janeway tries to activate the EMH and finds it has been disabled , and that the initialization routine has been locked with an encryption . It is proposed that by deactivating The Doctor , the alien forced the command codes back to Janeway . The captain suggests that because it is too dangerous for one person to have the command codes , they will be grouped and divided between herself and Tuvok . The two go back to the bridge to explain the situation , when the entity takes over Janeway and attacks Tuvok . A fight ensues . Tuvok tries to use his phaser but it is kicked from his hand by Janeway . Paris stuns the captain , and the entity jumps over to Kim , who pulls out his phaser to shoot Tuvok , but Paris knocks the phaser away from Kim and manages to subdue him . The alien then jumps to Durst , who manages to get a miscalculated shot off at Tuvok before being pulled back by another crewman . Tuvok then stuns everyone on the bridge with his phaser set to full spread . Act Four . In sickbay , Paris treats everyone ' s wounds with a hypospray while Kim tries to get The Doctor ' s program back on - line . Torres requests the captain ' s presence in engineering to explain that she found a discrepancy in the shuttle ' s internal sensor logs . After reviewing them , Torres explains that the logs weren ' t destroyed ; rather , someone erased them then overloaded the sensor matrix to make it appear they had been damaged . Further , Torres says that she was able to reconstruct the events in the shuttle . She was able to confirm that they were at the dark matter nebula , and that there was an energy discharge that came from the nebula itself , but that there was no ship . Janeway wonders why Tuvok would lie about that . She orders Torres to transfer controls for the magneton scan to the bridge once the sensors are ready to initiate the burst . On the bridge , Janeway asks Tuvok to locate the ion trail once again . Paris enters the bridge and tells the captain he has been studying the data The Doctor had been working on to discover the cause of Kes ' injuries and relays to her that they were actually caused by a Vulcan neck pinch . Janeway asks Tuvok to explain , and he says that he has no knowledge of the event and offers the entity as an explanation . But Janeway confronts him with the fact that the entity keeps attacking him , even on three different occasions . Tuvok blames Janeway ' s questions on paranoia , but she elaborates further that she is unable to pick up the ion trail he says he found . He directs the captain to search the alpha k band , where she finally finds the trail , but also notices the lack of any subspace distortion s in the trail ' s wake , and notes that according to the readings it would have come from a ship without engines . Tuvok confronts the captain , suggesting that she is under the influence of the entity and that it is trying to prevent " Voyager " from entering the nebula . Relieving Janeway of command , he orders Kim to take the ship in , but Kim refuses . Tuvok then warns everyone that his phaser is set to wide beam dispersal and to kill , before taking command of the bridge and huddling everyone in a group where he can see them . Act Five . Kim notices from a secondary console that the sensors are picking up highly coherent energy pulses with a biomatrix inside the nebula , suggestive of lifeform s , and that they are heading in " Voyager " s direction . Janeway asks Tuvok if the beings in the nebula are his people , assuming he is under the control of one of them , and Tuvok introduces them as the Komar and the nebula as their domain . Torres , in engineering , falls under the influence of the entity and ejects the warp core . She informs Janeway of what she has done , and Paris questions how it was possible of the alien to control Torres while it was controlling Tuvok at the same time . Kim suggests there may be two aliens on board . Then , Janeway realizes that Torres isn ' t authorized to eject the warp core on her own because that requires a command code authorization . She asks the computer who authorized the ejection of the warp core , to find it had been authorized by Commander Chakotay . The captain puts two and two together and realizes that the alien in Tuvok wants them " in " that nebula but that there is another presence that ' s been trying to keep them " out " and that it must be Chakotay who knows that they will be in danger if they go in there . She believes his neural energy has been displaced somehow and that as a result , he is able to move from person to person . Tuvok , upset at the turn of events , engages emergency thruster s . Janeway asks him whether the reason the Komar want " Voyager " is to extract everyone ' s neural energy . Tuvok explains that the collective neural energy of the crew would sustain his people for years to come . Janeway tells him that he doesn ' t have to do this and that maybe they can help them find another source of energy . But the ship keeps getting bombarded by the energy beams and , realizing that reasoning won ' t get them anywhere , Janeway uses this time to activate the magneton burst from the command console , disabling Tuvok and releasing the alien controlling him . Paris tries to steer the ship out of the nebula but can ' t be sure which direction they are really going because of the complex course Tuvok had been following . Kim goes to tactical to reconstruct Tuvok ' s navigational logs . The entity , now identified to be the displaced neural energy of Chakotay , inhabits Neelix in sickbay , who approaches the medicine wheel and rearranges the stones into a pattern that Paris is able to recognize as a map of the dark matter nebula , allowing them to chart a way out . After The Doctor successfully reintegrates Chakotay ' s consciousness , Janeway inquires as to what really happened in the shuttle . He explains he had the sensation of floating over his own body and thought he was dead . He couldn ' t speak or touch anything , but realized that if he could concentrate on someone in the same room with him , he could share their consciousness . He apologizes to Tuvok for having had to knock him around like that . Janeway welcomes him back but Chakotay says that he actually never felt like he had ever left . Memorable quotes . " " You might have asked before adorning my sickbay with animal remains . " " " " Find your way home , commander . " " " " If you feel at any time , that any of us are under the influence of the alien , you can countermand our orders and take control of the ship . Do you feel up to it ? " " " " Well of course , I make life and death decisions every day . " " " " I feel better already . " " " " Mr . Neelix , just because a man changes his drink order , doesn ' t mean he ' s possessed by an alien . " " " " Nevertheless , don ' t you think you should scan him or dissect him or something ? Just to make sure . " " " " I could examine every crewmember you ' ve mentioned so far , every person on board for that matter and it wouldn ' t do any good . From what we can tell the alien can jump from person to person at will . " " " " Sounds to me that you ' re " defending " Ensign Parsons . " " " " I ' m not defending him , I ' m just pointing out that you ' re acting a little paranoid . In fact , one could say that you ' re acting a little " too " paranoid . " " " " Captain I believe you are having a typically Human response to circumstances which are frightening and inexplicable ; commonly known as paranoia . " " " " According to these readings , it ' s a ship without engines . . . " " " " How did you manage to reintegrate his consciousness ? " " " " It involved three neural transceivers , two cortical stimulators , and fifty gigaquads of computer memory . I would be happy to take you through the process but it would take at least ten hours to explain it all to you . Needless to say it was a remarkable procedure . I would consider writing a paper about it , if there were a convenient forum in which to publish it . " Links and references . References . alpha k ; authorization code ; autopilot ; axon ; bio analysis ; biomatrix ; biomolecular scan ; bio - neural energy ; bio scan analysis ; ; bruise ; ; ; Burleigh ' s wife ; cape ; cardiostimulator ; central computer core ; Chakotay ' s tribe ; coma ; comb ; computer memory ; concussion ; condition four ; condition red ; cortical stimulator ; Coyote Stone ; dark - matter nebula ; ; dendrite ; density ; dilithium matrix ; DNA ; dissection ; dizziness ; drawing room ; emergency thruster ; England ; Fifth Realm ; forensic sweep ; garlic soup ; gigaquad ; Hargrove ; holocomic ; holodeck ; holonovel ; hostage ; house call ; Ilidarian ; intruder alert ; ion trail ; " Janeway Lambda one " ; Komar ; lemon ; lie ; logic ; lollipop ; long range sensor ; lord ; magneton scan ; magneton scanner ; main computer ; medical emergency ; medicine wheel ; memory engram ; Mountains of the Antelope Women ; multiphasic scan ; mutiny ; Native American ; navigational computer ; Navigational Control ; navigational log ; neural energy ; neural transceiver ; non - corporeal lifeform ; nostalgia ; painting ; paranoia ; parity trace scan ; ; pejuta ; phaser ; planetoid ; plasma relay ; psycho - spiritual belief ; sculpture ; security access code ; setting ; shuttlecraft log ; Sixth Realm ; Sora root ; star map ; subspace distortion ; talisman ; trianic energy being ; trapezius nerve ; vehicle status ; visual relay ; Vulcan mind meld ; Vulcan neck pinch ; waiting room ; warp core ejection