Tension reaches breaking point in the Norwegian Sea where a British frigate has clashed with a Soviet merchantman with tragic results. In retaliation the Russians close the Baltic to UK shipping but the Admiralty sends a freighter called 'British Venturer' - under her newly-promoted Captain Cable - to test the Reds' resolution. Or so it seems. And so Cable believes.

But only when his ship has been savaged by the Soviet Navy and impounded in the Baltic port of Ahldenstadt while he's contemptuously deported back home, does Cable discover that the world's worst nightmare has only just begun - that the apparently innocuous merchantman he'd commanded conceals a threat more horrific, more destructive than any aircraft or missile-borne weapon could deliver.