March 1967: HMS Temeraire is Britain's latest and most advanced nuclear submarine. But when the Temeraire's trials are cut short and she is ordered to the Far East to reinforce the British fleet against a threat from Red China, Captain David Jermain knows that this is no routine exercise in flag-waving. And once in Asian waters, he and his submarine find themselves involved in a hidden, undeclared conflict beneath the sea. While the politicians on land haggle over a situation that could hold the seeds of a full-scale war, Commander Jermain must keep his faith in himself and in his new ship's potential—even when ordered to take the Temeraire to the edge of a catastrophe.