The TARDIS arrives on a planet that has been turned into a space museum but the Doctor and his friends are puzzled when they find themselves out of phase with their surroundings.

Now back on their proper time track, the Doctor and his friends must work to avoid the future they saw for themselves.

With the Doctor missing, Ian, Barbara and Vicki find themselves in danger from the Moroks while the Xerons also try to make contact with them.

While Ian tries to force Lobos to release the Doctor from the museum, Vicki joins the Xerons in trying to gain the weapons needed to start a revolution against the occupiers.