The British Merchant Navy hospital ship San Andreas is en route from Murmansk to Halifax, Nova Scotia during World War II.

The first sign of trouble occurs when the ship's lights mysteriously fail just before a pre-dawn bombing attack that severely damages its superstructure and sinks its escort frigate.

With most of the senior officers dead and the captain incapacitated, bosun Archie McKinnon must take charge of the damaged ship and steer her to safety despite German aircraft, u-boats, stormy Arctic weather and sabotage by an unknown traitor on board.

[7][8] The Los Angeles Times said "This is MacLean at his unholy best, ripping our nerves, combining tragedy with dread as we race on, armchair victims of an overdose of shock.

[12] In 2016 Deadline reported that London-based Dancing Ledge Productions had acquired the rights to adapt MacLean's works into an event TV series, the first of which would be San Andreas.