To help with the housework, including washing up, Graeme has built a robot he calls EB-GB (Electronic Brain of Great Britain).
Graeme tries to determine a common link between the series of recent disappearances, even writing up all the information that he has about the missing persons on the blackboard.
Graeme has no idea what could be the common link, and it takes Bill to point out that all the missing persons are trombone players.
In contemplation of this fact, Bill plays the trombone in the park to see if he can find the answer to the riddle and also get taken, but nothing happens to him.
Graeme sets about devising an ingenious plot, which includes some "Supermen" and a "Supernun", to get rid of the rapidly approaching spacecraft before it can reach Earth.