is the sixth episode of the 19th season of Doctor Who , originally broadcast on January 19, 1982 . It is the second part of the four-episode serial Four to Doomsday , featuring Peter Davison as the Fifth Doctor. Plot Summary
: The Grecian philosopher Bigon reveals the ship's dark secret: almost all biological life has been replaced by android replicants. [S19E6] Four to Doomsday 2
The Doctor, Nyssa, Tegan, and Adric are aboard a massive spaceship belonging to the . In this second part: is the sixth episode of the 19th season