The TARDIS arrives near a vast Space Museum on the planet Xeros, but has jumped a time-track. The First Doctor, Ian, Barbara 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, but the most worrying is that the four travellers and the TARDIS are on display, with the Doctor and company in glass cases. A few moments later, the time track slips back and, the exhibit with themselves and the TARDIS vanish, but the travellers are still inside the Museum.