William Sylvester and Mai Zetterling star in this British crime drama. MI5 agent Layton (Sylvester) is brought in by Scotland Yard to help them catch an underground gang. In his new undercover role, Layton infiltrates the gang and helps them carry out their heists to get in with all the right people. After carrying out a million dollar jewel heist, Layton finds himself lured in by the criminal lifestyle. When his time with the criminals comes to an end, will Layton be able to return to his role with the force?