Radar is driving Hawk, B.J., Sherman, and Frank in a bus back from a "medical conference" when they get lost. They stop to see if they can find anything they recognize. When they decide to turn around, they find that the bus does not want to start. Radar goes off in the middle of the night for the latrine, and does not immediately return. Stricken, Hawkeye wants to set out to find him, only to be stopped by Sherman. An injured Korean surrenders to get medical help from Hawk and B.J.. Upon Radar return, the Korean helps repair the bus and get them out of danger.

The edge of the known universe, in the year 37,166. The TARDIS lands on the planet Zeta Minor, where a Morestran survey team has suffered a series of horrific killings. What dark secret does the team leader keep - and will the planet permit anyone to leave?