This series depicted the adventures of the secret crime unit of Scotland Yard, known as "The Ghost Squad," based on the real-life International Investigation Division of Scotland Yard.  The series (39 episodes airing from 1961 to 1964) starred Donald Wolfit (pictured with Angela Browne) as Sir Andrew Wilson, the squad's chief, and Michael Quinn as undercover agent Nick Craig.  In 1964, the series was renamed "G.S.5" for 13 episodes and featured a new agent Peter Clarke (played by Ray Barrett), who was assisted by Tony Miller, an agent from the earlier series played by Neil Hallett.