The TARDIS brings the Doctor, John and Gillian to the Time Museum of an ancient civilisation. Among the artefacts, they find what they think is a model of a Cyberman. It activates and calls others. The museum is a trap that will enable the Cybermen to kill their enemies. The Doctor destroys the Cybermen and one alerts others that will come. Finding Trod shells, they hid inside while more Cybermen come to look. Once they are at the far end of the museum they escape to the TARDIS.