The Doctor and Guin materialise on the Schrödinger Institute, a deep-space research station. The Doctor expects to see an old acquaintance, Tasdevin, who is working on a perpetual-motion machine. They wander the station for a while, and it seems to be deserted. They make their way to the huge central core housing the accelerator and laboratory equipment.
In the lab, the Doctor types at a keyboard, but many of the keys are stuck. Guin tries to lift some papers from a desk, but can only lift a few. She notices that an orange cup on the desk cannot be moved.
Suddenly, Tasdevin storms into the room. He throws some papers on the desk and starts typing on the keyboard. Groote enters after him, carrying an orange cup. Guin tries to apologise for their presence, but Groote passes right through her. She and Tasdevin start arguing, with Groote trying to convince Tasdevin not to continue with his experiment. He ignores her, and takes a box-like object with wires and connectors in it. He puts it in an open space in a standing obelisk. He pushes a button and turns to Groote, holding a knife. The lights flicker. Three men, van Ruysbroeck, Fauler and Suso, burst into the room, yelling for Tasdevin to stop. Tasdevin says, "Too late", and the obelisk explodes in a brilliant light.
Guin and the Doctor find themselves in the same room, alone. Events play out just as they did before, with the obelisk again exploding.
Once again the Doctor and Guin are alone. The Doctor theorises that Tasdevin's experiment has caused a temporal echo, and that the others are just echoes of the real people. Tasdevin and Groote enter as before, and the Doctor pushes at the orange cup after Groote has set it down. Guin notices, and when the three scientists burst in, she goes out through the door. When the next flash hits, she is in the corridor.
Guin wanders the station until she finds the canteen. The three scientists are on their way out. Guin enters the canteen and works at a computer until the next flash hits. The five scientists are now in the canteen. Fauler tries to convince Tasdevin to stop his experiments. Tasdevin leaves in anger when he realises that Fauler has been reading his personal diary. Groote leaves soon after. The remaining three discuss the situation, and Guin learns that all three men are from Galextricity Corp, which provides energy for Tasdevin's homeworld. Tasdevin's research is a threat to Galextricity. The three men leave, the lights flash, and another cycle begins.
Guin escapes the canteen by following Groote. She rejoins the Doctor, who has been looking at Tasdevin's notes. Tasdevin is trying to stabilise a portion of space-time, hoping it will constantly recycle and he will never age. The lights flash again.
As the next cycle begins, Guin casually mentions how they cannot touch anything that one of the scientists will use until the scientist is done with it. The Doctor realises the solution: he will switch the wiring in the obelisk at the last minute, after Tasdevin has touched it. When the time arrives, however, he can't reach the wires, so Guin has to support him on her shoulders. After he switches the wires, Tasdevin once again says, "Too late", but this time, the five scientists fade away. The Doctor says that once they leave the station, it too will fade away.
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- This story features a future incarnation of the Doctor who appears in many stories throughout many Short Trips anthologies, beginning in the short story Good Companions. All stories featuring this Doctor were written by Peter Anghelides, and he was eventually revealed to be the future Doctor first alluded to in the televised episode Battlefield under the alias of “Merlin”.
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