A plane circles the Lakeville airport, a plane hopelessly fog bound. Its pilot, a man who identified himself by radio as Albert Cross has already ensured the life of his thirteen year old son by sending him down safely in the only parachute aboard. Now op and Tank wait anxiously at the head of the runway for Cross to attempt the landing...

 The boy has parachuted to safety, but the plane crashes and Cross is killed. What is in the envelope that the boy had in his jacket? The boy has disappeared! The sy