Doctor Who: Logopolis (21/03/1981)

Synopsis

After an encounter with the Master, an airline stewardess named Tegan Jovanka becomes an unwitting stowaway aboard the TARDIS as it travels to the planet Logopolis. There, the Doctor discovers that the Master's interference with the Logopolitans' advanced mathematics has unleashed a wave of entropy which threatens to consume the entire universe.

Tom Baker

Matthew Waterhouse

Sarah Sutton

Janet Fielding

Anthony Ainley

Tom Georgeson