Dancing has become little more than a form of exercise, with no contact, partners, or anything remotely romantic allowed. Tim misses the days before this was so, and is on a mission to bring them back.
As trombone players everywhere mysteriously disappear, the Goodies try to make sense as to what is happening. They realize there are aliens out there. Bill wants to talk to them, but Graeme wants to destroy them.
Tim, Graeme and Bill are 2 year old boys during WWII. After leaving their parents to go to a school for intelligent boys, they are sent on an important mission to Germany.