The Time Monster ( TV story ) The Time Monster was the fifth and final story of Season 9 . It featured another explanation of the destruction of Atlantis ( 1967 ' s " The Underwater Menace " and 1971 ' s " The Dæmons " also offered explanations ) . This was also the penultimate serial to feature Roger Delgado as the Master and was the last story to feature the Master on " present day " Earth against the Doctor and UNIT . In addition to his use of hypnosis , the Master also demonstrated a newly seen ability to perfectly imitate another person ' s voice . This story marked the debut of the first redesign for the TARDIS console room , which was shared for both the Third Doctor ' s and the Master ' s respective TARDIS interiors . It featured heavy alterations to the original roundel design of the TARDIS interior set that had remained in use since 1963 , and a new time rotor prop . However , the exaggerated roundel design was subjected to criticism and suffered heavy damage during the filming break between season 9 and season 10 , necessitating the disposal of the new set and the construction of a second redesign that would appear in the upcoming season . Synopsis . , in the guise of Professor Thascalos , has constructed at the Newton Institute in Wootton a device known as TOMTIT — Transmission Of Matter Through Interstitial Time — to gain control over Kronos , a creature from outside time . The creature is summoned but proves to be uncontrollable . Plot . Episode 1 . The Doctor sits before the Master , who stands next to a crystal , laughing . Explosions resound . In UNIT HQ , Jo wakes the Doctor . He enquires if there have been any reports of volcanic eruptions or earthquake s lately . Elsewhere , the Master — or Professor Thascalos , as he calls himself — holds the crystal the Doctor saw in his dream . He ' s in a laboratory at the Newton Institute , working with Dr Ruth Ingram . The crystal , the Master claims , is no different than any other piece of quartz , yet it is . Stuart Hyde , a co - worker , enters . The Master leaves them to conduct further experiments . After he has left , Ruth says she doesn ' t know which is more annoying , " his dictatorial manner or that infernal courtesy of his . " At UNIT HQ , Mike Yates points out the Thera islands , where the quakes have struck . Jo mentions Atlantis , telling the Doctor that Thera is reputedly its location . The Doctor talks to the Brigadier on the phone and tells him to put out a warning to every UNIT section and HQ , because of a dream he had about a half hour ago . He says he is too busy to see the TOMTIT demonstration at the Newton Institute , so Benton is asked to go instead . At the institute , the Master hypnotises the Director , Dr Charles Percival , into believing him about his TOMTIT experiments and his credentials . In the lab , Ruth and Stu decided to run the test without " the Professor " . Outside , a window cleaner observes their efforts , having been distracted from his work . At UNIT HQ , the Doctor uses a time sensor to detect the Master . It shows a TARDIS in use . The experiment at the institute shows the jar at one end disappearing and reappearing at the other . Looking at the clock outside his window , the Master notices it has slowed down . The experiment is causing an overload , but Ruth and Stu contain it . Outside , the window cleaner falls from his ladder . The Doctor and Jo decide to follow the signal . They set off in Bessie . Back at the institute , the Master confronts Ruth and Stu , berating them for their foolishness . They tell him about the overload , and he tells them they were drawing power from outside time itself . Stu looks out the window ; a convoy is approaching with a UNIT Jeep in it . The Master tells Ruth and Stu to leave him to his work . The Doctor and Jo realise that the signal must be coming from Wootton , where the institute is . Using Bessie ' s super drive function , they speed along . UNIT arrive at the institute and find the window cleaner , alive but injured . The Brigadier , Benton , Dr Cook , his aide Proctor and Percival enter the control room with Ruth at the research station . Cook complains about his pheasant lunch and expenditures . The Master enters in a radiation suit , his features hidden . The test begins , and Ruth warns the Master that the power is overloading . Stu is in the crystal room . He gets too much power and can ' t control it . He calls to them to switch off . Ruth shouts the warning at the Master . The Master only yells out , " Come , Kronos , come ! " Episode 2 . The Doctor and Jo arrive in Bessie . Jo seems to freeze . The Doctor runs to the laboratory , where he orders Ruth to reverse the polarity and cut the power . They go to help Stu , only to find he has been aged to an eighty year old man . Different theories are suggested — radiation and a change in metabolism , both of which the Doctor denies . The Brigadier points out that the only thing that makes people age naturally is the passing of time ; the Doctor realises this is the explanation — Stu ' s personal time has been vastly accelerated . They learn that Professor Thascalos is the Master — Thascalos is Greek for Master . Stu wakes up and starts rambling . The Doctor demands he tell what he saw . With difficulty , Stu replies " Kronos ! " The Doctor and Ruth go back to the laboratory whilst the Brigadier orders troops from UNIT , as well as the Doctor ' s TARDIS . He tells Percival to order an evacuation of the building of all but essential personnel by 3 o ' clock . Meanwhile , Ruth shows the Doctor the crystal . He explains that outside space - time live creatures called Chronovore s , time eaters . Kronos is the most fearsome of the lot . The crystal is the original from Atlantis , which summoned Kronos . Long ago , in Ancient Atlantis , Kronos begins to stir . Percival finds the Master in his study and panics . The Master hypnotises him into not worrying and continues with his sums . Both the Doctor and the Master are confused about the earlier power build up , which logically shouldn ' t have happened . The Doctor discovers that the crystal has been moved through interstitial time . This means it really is the original crystal used to summon Kronos in Atlantis . The Master tricks Benton out of the laboratory by faking instructions from the Brigadier . Benton , however , climbs back in through the window , having seen through the Master ' s ruse . The Master knocks him out and summons an Atlantean priest called Krasis . Episode 3 . Whilst the Master orders Krasis to give him the secret to controlling Kronos , Benton escapes and warns the Doctor . Kronos is summoned and devours Percival . The Brigadier , Benton and Ruth run towards the lab and begin to run in slow motion . The Doctor notices what is happening and pulls them out of the time field . Stu ' s ageing is suddenly reversed , returning his age to twenty - five . The Doctor orders them all back inside . The Master returns Kronos to the crystal , which Krasis claims is but a portion of the original . In Atlantis , Hippias asks Lord Dalios if the time has come for Kronos to return at last . Dalios is old enough to remember the time of Kronos and fears his return . He shows Hippias the true crystal , which is guarded by a " horrible " creature . The Doctor cobbles together a time flow analog , which works like jamming a radio signal . It works until the Master uses the TOMTIT device to overload it . He sets about delaying the convoy from UNIT , using a medieval knight , a troop of Roundhead s , and finally , a German V1 " doodlebug " bomb . The Brigadier , Jo and the Doctor watch as the bomb explodes where the convoy is . Episode 4 . The Doctor , Jo and the Brigadier go to meet the convoy . Fortunately they are unharmed . Ruth , Stu and Benton go to the laboratory to stop the Master . The Doctor and Jo follow in the Doctor ' s TARDIS , using the time sensor as a homing device and placing the Doctor ' s TARDIS inside the Master ' s . The Doctor explains that if the frequency of the two TARDISes is too high , even by a fraction , a time ram will occur , resulting in utter annihilation . This does not dissuade Jo , so they take off . They end up stuck in a space loop with the Master ' s TARDIS — if they enter one , they come out into the other . The UNIT convoy arrives at the institute , but the Master freezes them in space - time . Krasis and he escape into the TARDIS , leaving Benton , Ruth and Stu trapped inside the building . As this is going on , the Master taunts the Doctor , pointing out that he could easily throw his enemy into the Time Vortex and refusing to listen to the Doctor . When the Doctor forces the sound of his voice through to the Master ' s TARDIS , the Master feeds the words back to him and makes them come out as garbled nonsense . In the lab , Ruth and Stu try to turn off the machine . It has no effect on the Brigadier and his men , who are still frozen , and Benton is regressed in age to a baby . With no other options , the Doctor orders Jo to close the door behind him when he steps into the Master ' s TARDIS . Yet again the Master refuses to listen to reason and summons Kronos , who devours the Doctor . The Master sends Kronos back into the crystal and breaks the lock on the Doctor ' s TARDIS , sending it and Jo tumbling through the Vortex . Episode 5 . Jo hears the Doctor calling to her , along with many other whispering voices . He explains they are his subconscious thoughts and tells her not to listen too closely . The TARDIS is relaying his thoughts to Jo ; she follows his instructions and pulls a red handle on the third control panel , allowing the TARDIS to pull the Doctor out of the Vortex . In Atlantis , Dalios holds court . Hippias speaks to the king , saying the people wish for the blessings their ancestors enjoyed under Kronos . Dalios tries to convince his people that Kronos was a curse . The Master arrives in his TARDIS , bringing Krasis with him . Krasis says he has seen Kronos . Dalios takes the Master and Krasis with him to discuss the matter . Later in the courtyard , the TARDIS materialises . The Doctor and Jo are confronted by Hippias and Krasis , who calls the guards . The Doctor and Jo are taken to the king . The Master tries to hypnotise Dalios but fails . He is sent away , and to his surprise sees the Doctor and Jo being brought to the king . The Doctor and Jo meet the king , and Jo is brought to Galleia . The king asks for the Doctor ' s help to save Atlantis . Galleia and the Master meet to discuss the crystal , with Jo eavesdropping on their conversation . The crystal is in a maze guarded by the Minotaur . Galleia sends Hippias to retrieve the crystal . Jo follows them while Lakis goes to tell the king and the Doctor . Krasis catches Jo and puts her in the maze . She hears a loud roaring . . . Episode 6 . Hippias saves Jo from the Minotaur but is killed in the process . The Doctor arrives and bull fights the Minotaur . It falls in a pit , breaking open a wall to a hidden chamber . The Doctor and Jo find the Crystal of Kronos waiting inside the secret room but are caught by Krasis , who takes the crystal . The Doctor demands to be taken to the king but is taken to the Master , who has taken over with Galleia ' s help . The Doctor and Jo are imprisoned . The Doctor tells Jo about his hermit friend . Dalios is put in the cell with them and dies there . Galleia presents the Master to the council . The Doctor and Jo are in attendance . The Master announces he will bring Kronos . Jo tells Galleia that the king is dead . Galleia orders the Master seized , but Krasis summons Kronos , whom the Master orders to destroy Atlantis . Jo tries to stop the Master but is taken to his TARDIS , which dematerialises . The Doctor escapes into his TARDIS . The Doctor contacts the Master and threatens him with a time ram . The Master calls his bluff , but the Doctor gives him one last chance . Jo pleads with the Doctor to do it , but when he says there ' s another way , Jo pushes the button , causing the time ram . Both TARDISes are in a featureless place . Jo thinks they ' re dead , but the Doctor isn ' t sure . Suddenly a large female face appears . She is Kronos , and she was freed when the two TARDISes collided . She is grateful for the Doctor ' s help and plans to keep the Master to torment him . The Doctor asks to take the Master with them , and Kronos agrees . However , the Master makes a run for his TARDIS and escapes . Back in the lab , Stu takes care of baby Benton while Ruth works on the machine . The TARDIS lands back in Cambridge . The machine finally releases the Brigadier and his men , then it overloads . The soldiers enter the room , believing the Master is still there , only to find him long gone . The Brigadier questions Jo ' s strange Atlantean getup , a spontaneous change from his point of view . However , Stu goes to check on the baby Benton , finding nothing but the clothes he shrank out of . Then , a man rises up from the floor . To everyone ' s surprise , Benton has returned back to his original age . . . only he ' s no longer sporting his uniform , but his birthday suit . Home video and audio releases . DVD releases . It was released as issue 137 of " Doctor Who DVD Files " . Digital releases . This story is available : VHS releases . This story was released in the UK as " Doctor Who : The Time Monster " in November 2001 ( as part of the Master box set which also contains " Colony in Space " ) .