Jocelyn and Rupert Middleton's 17-year-old daughter Vivienne has gone missing. She has an American boyfriend called Bobby Wilson that her parents do not approve of. They think he is only in the country to avoid the draft for the Vietnam War. But Bobby has not seen her either. Someone steals a bronze sculpture from Sir Piers Radley's estate and another one from Lord Ashfordly. They have even taken his lordship's gates and he wants some action - now. David is cleaning up the shed and finds a metal detector. He gives it a good clean, a bit of oil and a new battery and is ready to go treasure hunting. At first Aunt Peggy thinks he is talking nonsense, but she changes her mind after a small demonstration.