It is May 1944, two weeks before D-day. Britain stands poised for the long-awaited invasion of France - thousands of troops wait anxiously for the orders to come for embarkation. MI5 is horrified to discover the top-secret codewords for the invasion suddenly appearing as clues in the Daily Telegraph crossword. Two agents are immediately dispatched to confront the culprit, the headmaster of a boys' school in southern England.
| Actor | Role |
|---|---|
 Michael GoughMr Maggs | Mr Maggs |
| MMichael QuillReg | Reg |
| DDemetri JaggerDennis | Dennis |
| JJacob KrichefskiNorman | Norman |
 John CarsonLauderdale | Lauderdale |
 Paul BrookeLilliwhite | Lilliwhite |
| IIan ThompsonMeadows | Meadows |
| SSally NodenJennifer | Jennifer |
| EEliza HuntMrs Anderson | Mrs Anderson |
| CCharles LewsenMr Bellows | Mr Bellows |
 Frank WilliamsMajor Sykes | Major Sykes |
 Alan DavidMr Smout | Mr Smout |
| VValérie ChassigneuxMademoiselle Gidoux | Mademoiselle Gidoux |
| SStephen HoyeLieutenant Hipwell | Lieutenant Hipwell |
 Bradley LavelleKopanski | Kopanski |
 James AubreyColonel Mitchell | Colonel Mitchell |
 Roger BrierleyAir Vice Marshall | Air Vice Marshall |
 Peter HowellChurchill's Secretary | Churchill's Secretary |
| JJames ApplebyHome Guard Man | Home Guard Man |
| TTristram DaviesGieves | Gieves |