Ceremony of the Keys (London) passes his lantern to a soldier, and marches with his escort to the outer gate. The sentries on duty salute the Queen’s Keys as they pass. The Warder first locks the outer gate and then the gates of the Middle and Byward Towers. The Warder and escort march down Water Lane, until they reach the Bloody Tower archway where a sentry challenges the party to identify themselves: The Warder and escort march down to the foot of Broadwalk Steps where the main Tower Guard is drawn up to meet them. The party halts, and the officer in charge gives the
The Keys of Marinus weapon, and Ian is freed. The travellers return to Arbitan's island, where Altos and Sabetha have been held prisoner by Yartek—Arbitan's killer—and the four keys have been seized. The Doctor frees Altos and Sabetha and unmasks the Voord. Ian gives Yartek a false key found in the screaming jungle; when Yartek places the key in the Conscience, the machine explodes and he is killed along with the occupying Voord. The Doctor, Susan, Ian and Barbara flee the tower with Altos and Sabetha before the growing blaze overtakes the ancient structure. "The Keys of Marinus" was written to replace a different