Having entered the Matrix to try and track the Master, the Doctor tries to deny its reality but eventually decides to take on the Master’s plans within the reality of the Matrix.
All sorts of weird things happen in the somewhat hallucinatory Matrix – evil traindrivers, masked hunters – and a biplane chase that takes its cues from ‘North by Northwest’ (or, perhaps, its earlier incarnation, ‘The 39 Steps’).
This epsiode has one of the most complained about cliff-hangers ever. Often praised, it was also heavily criticised, and Mary Whitehouse (a self-styled moral crusader) thought it one of the most frightening scenes in Doctor Who because children would have to wait a week to find out what would happen next. In response it was actually cut from the master tape, but has subsequently been restored.