The Brigadier moves into his new headquarters, which he soon discovers is haunted by several ghosts. There's a screaming soldier who bursts into flames before vanishing, an Egyptian held over from the house that used to be there. And then there's an older man, who the Brigadier knows only too well...
Giles has stumbled on a cache of documents relating to the life of one of his role models, Alistair Gordon Lethbridge-Stewart, in P.R.O.B.E.'s files. Aware that some "busybody" will likely eventually try to take them back under the Official Secrets Act, and wanting to be able to truthfully say that he did not photocopy the documents while still retaining the data, he sets about recording himself reading them aloud. The first document is an account in the first person of Alistair's first day at his force's new headquarters.
According to it, strange occurrences start quickly as the Brigadier's men attempt to settle into their newly-allotted new H.Q., in a large estate which formerly belonged to an amateur egyptologist until the house burned down. As Captain Summerfield reports, a mysterious uniformed Private was twice seen appearing near "real" soldiers just long enough to scream in anguish and burst into flames, before vanishing again. Another ghost is soon added to the list, an Egyptian man in Edwardian clothing seen walking down a corridor with purpose, before simply vanishing.
With the settling-in not yet done at ten in the evening, the Brigadier decides to sleep in the day-bed in his office, leaving Captain Summerfield in charge. However, as he prepares to go to bed, a third apparition arrives, a man whom the Brigadier at first thinks to be his father. He instead soon clarifies that he is the Brigadier's own future self, transported back in time from his first day of retirement by unknown forces. The older Brigadier explains that the other two ghosts are also "misplacements", moments in the two men's lives which have become separated from their normal time-stream and looped for eternity. He notes that the two "ghosts" continue to periodically appear, harmlessly, in the headquarters throughout the decades to come, and advises his younger self to use them to test the mettle of his men in the face of blatantly supernatural happenstances.
Pondering the odd fact that the older Brigadier doesn't remember their encounter from his younger self's perspective, the two realise that their encounter appears to be a deliberate diversion to keep the younger Brigadier busy while something happens. Heading out of the room with weapons drawn, they find Summerfield's lifeless body on the floor of the Duty Office, his neck bent at a lethal angle. Continuing to advance through the building, they bump into night-sergeant Hodges, who reports to their great shock that he's just seen Captain Summerfield in the break room.
Indeed, what appears to be a healthy Captain Summerfield is making himself tea in the break room when the two Lethbridge-Stewarts get there. However, when the younger Brigadier orders him to get out of the room so that they can investigate which of the dead and living Summerfields is real, the man is reluctant, allowing the older Brigadier to guess that he is an impostor; the real Summerfield, as he knew him for all those future years, was unfailingly obedient to military discipline. Shooting at the impostor, they reveal him to be an extremely lifelike android who finally malfunctions and "dies" when the future Brigadier upends the tea urn on him, causing him to short-circuit. The older Brigadier, examining the deactivated robot, recognises him as one of the creations of Deller, a malevolent scientist he faced in his past and the younger Brigadier's future, and who apparently tried to get his revenge by sending this robot back in time to blow up a younger Alistair on his first day at the headquarters from which he was to foil Deller's schemes.
After some parting words during which the older Brigadier points out that the younger Brigadier's future is once again open and unknown despite their encounter, as Summerfield's absence will doubtless alter future events, the future Brigadier vanishes from this time-zone. The younger Brigadier is left to hope that his future self is back to his quiet retirement after this last adventure — and reasons that, all in all, he rather enjoyed his first.
- The Brigadier
- Captain Summerfield
- Lieutenant Watson
- The Screaming Soldier
- The Solitary Egyptian
- Sergeant Hodges
- Robot Summerfield
- Giles claims that any more detail about himself than his name being "Giles" and his working for P.R.O.B.E. are protected under the Official Secrets Act.
- Captain Summerfield being murdered constitutes a change of the Brigadier's timeline because the man was meant to be the Brigadier's aide for "fifteen years".
- Reference is made by the older Brigadier to an enemy called Deller who created robot duplicates.
- There are "tales" of the building's last owner before it passed into government property "being killed by the curse of King Tut or some such thing".
- The Brigadier recollects Korea.
- While not explicitly named for licensing reasons, the new headquarters are implicitly the UNIT HQ. Accordingly, references are made to the fact that these headquarters were built on the remains of Marcus Scarman's estate: a reference to the old building burning down as seen in Pyramids of Mars is made, and one of the "ghosts" resembles Ibrahim Namin.
- The older version of the Brigadier recalls his scientific advisor, a strange man who'd often make "faintly alarming" comments to him about the nature of Time. (TV: Spearhead from Space)
- Anne Travers is the younger version of the Brigadier's current scientific advisor. (TV: The Web of Fear)