(BARBARA manages to reach the key but as she takes it there is a grinding of gears and the arms of the statue close in around BARBARA'S legs.) (He tries to turn the handle on the door.) After a brief pause she moves over to a door on the other side of the room.) BARBARA: (Calling.) BARBARA: Oh, the travel dial. IAN: Biology seems to have been his field as far as I can make out. Into the building I suppose. LABORATORY
(IAN and BARBARA find themselves in a laboratory, the tables of which are full of books and all kinds of plants. Only those ... warned by Arbitan could avoid them. Where is the micro-key?
Plan: A: The TARDIS; Q: What is the name of the Doctor's time machine? A: Marinus; Q: What is the name of the planet? A: glass; Q: What is the island made of? A: acid; Q: What is the sea made of? A: the elderly Arbitan; Q: Who forces the travelers to retrieve the keys? A: Arbitan; Q: Who is the keeper of the Conscience of Marinus? A: Voord; Q: What is the name of the race of warriors that Yartek leads? A: its originally benevolent mind-influencing power; Q: What is the original purpose of the Conscience of Marinus? Summary: The TARDIS arrives on the planet Marinus on an island of glass surrounded by a sea of acid. The travellers are forced by the elderly Arbitan to retrieve four of the five operating keys to a machine called the Conscience of Marinus, of which he is the keeper. These have been hidden in different locations around the planet to prevent them falling into the hands of the evil Yartek and his Voord warriors, who plan to seize the machine and use its originally benevolent mind-influencing power for their own sinister purposes.