Deep space, an unknown time - on course for Gallifrey, the TARDIS passes through a strange disruption. When they materialise, the scanner shows the Time Lord homeworld... but the travellers have passed into the negative pocket universe of E-Space and... (more) are in fact on the planet Alzarius, where evolution works very differently...

Andrew Forbes, Barney Lawrence, Bernard Padden, George Baker, June Page, Norman Bacon, Richard Willis, Tony Calvin