Part NineSeries Episode Number: 648
World Premiere: Sat 1 Nov 1986 - 5:47pm GMT [BBC One] (United Kingdom)
First Broadcast: Sun 11 Dec 1988 - 11:00pm CST [WTTW 11 Chicago]
Running Time: 24 minutes 56 seconds
5.20 Million (UK)Appreciation Index: 66 (UK)
Chart Position: 85 () (UK)
The Doctor and Mel are taking a rest aboard the Hyperion III when a series of murders lead them to suspect there is more to Professor Laskey's party than initially appears.