The final six episodes of Timeslip, written by Victor Pemberton, incorporated a sketch reminiscent of Da Vinci’s Vetruvian Man into the opening titles. As the ominous tones of Edouard Michael’s Rite de la Terre fade the caption tells us this is The Day of The Clone.
The strands of the first three serials begin to knit together. In the previous episode, Liz Skinner (Cheryl Burfield) had attempted to use the Time Barrier to return to help her future self, Beth. Except she has been drugged and kidnapped by the increasingly malevolent Commander Traynor (Denis Quilley). She now wakes locked away in a room without any windows.
Simon Randall (Spencer Banks) attempts to visit Traynor at his Whitehall office but is refused entry. Before he leaves, Traynor’s secretary lets slip that something is being tested at R1, a secret laboratory managed by the commander.
This secret establishment was established by Morgan C. Devereaux (John Barron) to develop the longevity drug HA57 that was being tested in The Ice Box. Traynor is listening to tape of Liz describing her time travels. A doctor at R1 remonstrates with Traynor that it is not benefiting the people on which it is being tested. Their condition is deteriorating. Traynor dismisses this, adding it is early days. The doctor also disapproves of using 15-year-old Liz in the trial after learning she has been subjected to hypnotherapy.
Simon sneaks into a mail van that is going to R1 and breaks in. Sneaking around, he sees old people walking aimlessly round the corridors. One of them seems to know Simon. He ducks out os sight when Traynor exits an office, recognising his assistant as one of the Technocrats from The Year of the Burn Up.
Simon ducks into Traynor’s office and looks through the Technological Master Plan, a book by Deveraux, and listens to some of the recording of Liz. As he leaves the old woman looks shocked to see him. Her name is Maria (Mary Larkin) but she says she has lost her identity. She has been at R1 for five years as a volunteer. She reveals they all spend time in the room without windows, describing it as savage.
Maria distracts a guard allowing Simon to take an elevator to the room. However Liz hits him over the head when he opens the door. Traynor is operating on one of the volunteers. Liz and Simon start to escape but an alarm sounds. Maria shows them a laundry shute that allows them to get outside. R1 is near the old Naval Base at St Oswald. As Traynor and his men advance, they duck through the Time Barrier.
Liz and Simon find themselves in Simon’s home. Except everything seems terribly new. After an awkward conversation with Mr Randall, the realise it is the past and run off before an 11-year-old Simon comes don the stairs. Liz laughs at the squeaky voice they can hear.
At the R1 of 1965, Traynor bumps into a young woman, knocking her over. He apologises and helps her back up. She is a volunteer saying she thought she owed a debt to society but is now beginning to think she has paid it. Traynor looks concerned as they part.
Traynor storms into an office where Deveraux, very much alive, is running through test results. The Commander is outraged that he is using human test subjects. Deveraux says he feels he doesn’t need to ask permission. Traynor replies bluntly that he does. Deveraux says he is tired of moralising. Traynor reveals that he made a written undertaking to the Home Secretary that no human subjects would be used. Deveraux dismisses this with contempt, prompting Traynor to threaten to have grant money for the project withdrawn. Oops, that’s got his attention. Deveraux believes that mental conditioning is an essential part of the longevity treatment. Traynor disagrees. He demands the volunteers be sent home.
Liz and Simon break back into R1 but get caught in the induction for the volunteers. They subsequently hide in a treatment room where some of the volunteers have been dressed in Regency clothes. Deveraux subjects the room to a sonic pulse. Traynor is appalled but finds himself locked in the observation room which fills up with a thick gas.
Deveraux returns to remove the unconscious Traynor. He turns off the sonic device much to the relief of Liz and Simon. Traynor wakes in an oxygen tent unable to move. Meanwhile, Liz and Simon befriend Maria - who is a young woman. They promise Traynor they will help but are caught and subjected to a hypnotic processing treatment.
During this treatment Liz makes telepathic contact with her mother in the future. The hypnotist employed by Devereaux tells them time is no barrier, they are of one mind. The past, present and future are one.
Liz wakes in a room with Maria. She and Simon have not been affected by the treatment (but in the future Jean is in a trance). Maria helps Liz and Simon escape. They try to warn Traynor’s superior but to no avail. returning to the present they find evil Traynor and his men are waiting for them.
They are locked up once more. but Simon confronts Traynor over the fate of the HA57 volunteers. They have aged at an accelerated rate in the last five years and this shows no sign of changing. Traynor leaves them locked in the room. Liz says she can’t understand how Traynor could change so much, but Simon recalls something they were told in the Ice Box. There is only one possibility, the man they have known since their first time trip is a clone!
Clone Traynor has been carrying out the work required to make Devereaux’s vision a reality. Frank and Jean have gone to the Naval Base. She tries to sense Liz but only gets an impression of Traynor.
Liz and Simon break out with the help of the doctor who was arguing with Clone Traynor earlier. They find a sealed room. Opening the door, they discover the real Traynor who has been a prisoner since 1965.
Everyone converges at the Naval Base near the Time Barrier. Liz is reunited with her parents and the two Traynors stand face to face. The clone asks the other man who he is. Traynor says he is the past and the future. The clone declares that he is working for the future and his work must go on. It can’t be stopped.
Real Traynor tells his clone to find his own future. At which point a strange force starts pulling at everyone, knocking them down. It has a bigger effect on the clone, dragging him into the invisible barrier. He clutches at the grass, but cannot resist the pull. he is dragged screaming into infinity. Real Traynor speculates that the clone may still be out there.