It stars Roger Moore, Telly Savalas, David Niven, Stefanie Powers, Claudia Cardinale, Richard Roundtree, Sonny Bono and Elliott Gould.

The camp Commandant, Major Otto Hecht, a former Austrian antiques dealer, is sending some of the valuable pieces to his sister living in Switzerland.

While Hecht is content to sit out the war, the SS Commandant of the nearby town, Major Volkmann, brutally enforces discipline, including reprisal executions of civilians.

Zeno, who is in contact with Allied Headquarters, is ordered to break the prisoners out of their camp and use them to help liberate the town and capture the nearby U-boat refuelling depot.

After completing the mission, Charlie asks Zeno to lead him and two other prisoners, Judson and Rotelli, up to the monastery on Mount Athena to steal Byzantine treasures kept there by the monks.

Zeno now receives word from Allied intelligence that the planned invasion of the islands has been brought forward, and so the German garrison in the monastery atop Mount Athena must be neutralised.

Professor Blake learns from one of the freed monks that their treasure — Byzantine plates made of gold — is safe, having been hidden in the brothel the entire time.

The final scene cuts to the modern day, by which time Zeno's former headquarters have been turned into a state museum housing the treasures of Mount Athena.

William Holden, who was in a romantic relationship with Stefanie Powers at the time, makes an uncredited cameo as an American sergeant, commenting that he has not escaped as he has a comfortable life as a prisoner (an inside joke referencing his role in Stalag 17).

[7] William Holden was visiting his girlfriend Stefanie Powers during filming and was persuaded to make a cameo in the prison camp scene, presumably reprising his role as Stalag 17 escapee Sergeant Sefton.

Grade had wanted an action film and felt it "did not live up to expectations of the script" turning out to be "a broad comedy with action-adventure sequences and the combination just didn't work."