Modelled on official reports, the action of this story occupies eight hours of a Sunday night/Monday morning in early autumn of 1943. The German U-boat supply ship, Heilbronne, is sailing heavily escorted from Le Havre to the Atlantic, and a mixed force of British motor gunboats and motor torpedo boats is ordered to intercept and sink her. Amongst them are Ben Quarry, the Australian navigator of MGB 875, whose girlfriend Rosie is an SOE agent, and the CO, Bob Stack, whose wife is having an affair with a fellow officer. So as dawn breaks and the survivors limp home, many issues remain to be resolved.