The TARDIS arrives near a vast Space Museum on the planet Xeros, but has jumped a time-track. The First Doctor, Ian Chesterton, Barbara Wright and Vicki have a series of bizarre experiences as they venture outside and into the Museum – not least that they see but cannot be seen by the militaristic Moroks who run the museum, or the servile indigenous Xerons who work for them. The museum contains fascinating exhibits, including a Dalek shell as shown in the picture, but the most worrying is the four travellers themselves encased and on display. Quite soon afterward the time track slips back and, though the exhibits of the TARDIS and the four travellers vanish, they still find themselves inside the Museum.
The head of the Moroks, Lobos, is a bored and desperate museum administrator and colony governor, who reflects sourly that the glories of the Morok empire are past. Like Rome, the Empire became decadent and then declined. The Moroks have found the TARDIS and now start tracking down the occupants who have, as usual, become separated. The Doctor is the first to be found, but evades their interrogation tactics.
Meanwhile, Vicki has made contact with the Xerons and, hearing of their enslavement, aids them in their plans to stage a revolution. They attack the Morok armoury and Vicki outwits its controlling computer. With their new weapons, the Xerons are able to begin a revolution which slowly takes hold.
Ian has meanwhile freed the Doctor from Lobos, who had begun the process of freezing him and turning him into an exhibit. Ian and the Doctor are quickly recaptured by the Morok guards, and Barbara and Vicki are captured shortly thereafter. With all four held prisoner in the Museum, it looks like the time track prediction of their future as museum exhibits will soon be realised after all.
Help comes from the Xeron revolutionaries, who kill Lobos and the other Morok captors. The Xerons then go about destroying the hated Museum as the TARDIS crew slips away. They take with them a time/space visualiser as a souvenir. On the planet Skaro, their departure is noted by the Daleks….