Arriving on the planet Marinus the TARDIS the time travelers are unwittingly recruited to find the keys to the Conscience of Marinus, which have been scattered across the planet, to prevent from Voord, Yartek from taking over the planet. A Voord lies in wait to ambush an unexpected Susan Cast William Hartnell (The Doctor), William Russell (Ian Chesterton), Jacqueline Hill (Barbara Wright) Carole Ann Ford (Susan Foreman), George Coulouris (Arbitan), Francis de Wolff (Vasor), D