HMS Royston, Coastal Forces Depot Ship, is mother ship to a battered, war-worn bunch of MTBs and MGBs. New on board is Sub-Lieutenant Royce: commissioned for three months, sea experience three months in an Asdic trawler and aged 20. His commanding officer is Lieutenant Harston, aged 23.

His predecessor has been killed in action 48 hours earlier and is now hardly remembered. The crew are all young - some very young - but all old before their time …