Ruck

 was a homeless citizen of a tower block. They hadn't seen anyone else until the Seventh Doctor, Ace and Melanie Bush turned up. He tried to warn Ace and Mel about going into a lift. He later told the Doctor about how the tower went into constant night and how the inhabitants become Zombies. He had a brain tumour and Isobel thought that this was protecting him. (AUDIO: The Dispossessed)