A middle-aged couple, Terry and Gill Conroy, driving an expensive Jaguar, break down in a residential street, outside the house owned by George and Irene Boxall. The Boxalls offer them a cup of tea while the Conroys wait for the breakdown truck to arrive. In recompense, Terry Conroy invites the Boxalls to join them at a Tyrolean night.

But all is not as it seems. When the Conroys never turn up at the Tyrolean night (which is being held at Woodcote Park), George and Irene become suspicious and ask Ken for help.

A mysterious young woman, Meryl Spicer, turns up at Woodcote Park, looking for Helen. She claims to be Helen's long-lost daughter whom Helen had given away for adoption (!)

It turns out that the Conroys used the Tyrolean invitation simply as an excuse to get the Boxalls out of their house, with Meryl at Woodcote Park to alert the Conroys as soon as the Boxalls leave to come home. The reason for this subterfuge is that Tom Vallance, a bank robber, had hidden some plans in the Boxa