A gap the shape of the sixth piece. DOCTOR: And the chronodyne chip? DOCTOR: It's the Key to Time. It belongs to the Doctor. Neither is this Zeos. ROMANA: What about between Atrios and Zeos. That's the trouble with machines.
Plan: A: the Zeos world; Q: K-9 communicates with the leader of what world? A: the Doctor; Q: Who tries to stop the leader of the Zeos world from completing its plan? A: the unknown world; Q: What do the Doctor and companions discover between Atrios and Zeos? Summary: K-9 communicates with the leader of the Zeos world and the Doctor attempts to keep the leader from completing it's plan. The Doctor and companions discover the unknown world that is between Atrios and Zeos.