What is the connection between a music professor and the task of rendering mines safe? That is the question the Royal Navy's Commander (Mining) has to ask when he interviews applicant Vincent Reid.

It is March, 1940, and Hitler has unleashed the first of his secret weapons, the magnetic mine, against Britain. They fall by parachute, many drifting on to dry land, where they cause large-scale disruption. The menace must be overcome, and Vincent is put to work despite the Commander's misgivings.

With minimal training, he approaches each development analytically and with absolute precision. One development that catches him unawares, however, is the arrival of Hazel Wythenshawe from the Ministry of Information, but they soon rise above the initial awkwardness, and the two become mutually supportive.

As the mine menace continues, Vincent works flat-out, realising that that the odds against his survival are shortening all the time.