Castrovalva: Part Four 1982
7.3 273 The Doctor discovers Castrovalva is a cursive occlusion, an impossible yet manifested Escheresque environment, with all pathways, no matter which direction one goes, leading back to the same point. It is a trap laid by the Master with no apparent way out.
Runtime: 24 min
Starts: Peter Davison, Janet Fielding, Sarah Sutton, Matthew Waterhouse
Director: Fiona Cumming