二战时期，英军准备攻击一个重要的德国U艇基础，但行动的安全保密工作非常重要。半纪实性的影片在告诉人们，为减少不必要的伤亡，保密工作是多么的重要
Mervyn Johns
No 23: Mr Davis
Nova Pilbeam
Beppie Leemans
Reginald Tate
Maj. Richards
John Chandos
No 16
Stephen Murray
Mr. Barratt
Jack Hawkins
Brigade Major Harcourt
Geoffrey Hibbert
Pvt. John
Philip Friend
Lt. Cummins
Phyllis Stanley
Miss Clare
Mary Clare
Mrs. Webster
Basil Sydney
Naval captain
Joss Ambler
Mr Vemon
Brefni O'Rorke
Brigadier Blunt
Alexander Field
Pvt. Durnford
