The Chief Caretaker was the leader of Caretakers in Paradise Towers.
Unknown to his staff, the Chief had found a creature in the basement and made it his pet. He had the cleaners take it the bodies of the dead, believing that it ate them. The Chief even had Caretaker 345/12, subsection 3 killed to feed the creature. He thought of himself as the creature's "daddy".
When the Seventh Doctor was brought to him, the Chief thought he was the "Great Architect", namely Kroagnon, who designed Paradise Towers. He ordered his execution and was called away after a report on the death of 345/12, subsection 3 came in. When he returned, he found the Doctor had escaped and blamed the Deputy Chief Caretaker, who was tasked with his re-capture.
The Doctor was again brought before the Chief who began interrogating him. He soon learned the Doctor was not the "Great Architect" as he had thought, but still ordered his execution. Once again he was called away after a report on the death of Tilda and Tabby came in. He went to the scene of the death and bribed Maddy by offering her the flat in return for her silence on the matter.
While making his way back to control, he met with Cleaner 479, who forced him down to the basement. There he was brought before the creature, who revealed itself as Kroagnon. He needed a body to escape from his imprisonment. The Chief was forced into a container and corporelectroscopy was performed to transplant Kroagnon's mind into the Chief, effectively killing him. (TV: Paradise Towers)