The opening episode takes place in June 1940. Captain Pat Grant (Edward Hardwicke) is captured and taken to a camp where he immediately starts organizing escape activity. After an unsuccessful escape he is sent to Colditz.

Colditz gets a new senior British officer, Colonel Preston (Jack Hedley). (The previous senior British officer, Major Donaldson is referred to in this episode but never seen). On his arrival he witnesses a futile escape attempt by Flight Lieutenant Carter and when the Kommandant meets him, he believes Preston is a man of honour who he can deal with. The colonel's new orders that seem to be appeasing the Germans cause conflict and dissension in the ranks, but there is method in the colonel's madness, which could come unstuck when a Polish officer decides to escape.

When a lorry drives into the Castle courtyard, Captain Grant seizes the opportunity to put a blitz escape operation into action.

Wing Commander Marsh assists the British doctor as an orderly and he proposes escaping by feigning mental illness in order to be repatriated. The escape committee is not told of the plan and Marsh starts acting irrationally – however, the ever suspicious Ullmann appoints Private Hartwig to watch Marsh. Hartwig has a mentally disturbed brother and knows exactly what to look for. Will the wing commander be able to live the part and convince him?

Mc Donald, a Scottish officer, receives a ""dear John"" letter and wants to escape desperately to put things right at home which puts the escape committee in a spot. Phil Carrington befriends the man and does what he can to help, but McDonald is tall and loud and stands out in a crowd – will anyone want to escape with him?