The mine is an impartial killer, and a lethal challenge to any volunteer in the Special Countermeasures of the Royal Navy.

They are brave, lonely men with something to prove or nothing left to lose. Lieutenant-Commander David Masters, haunted by a split second glimpse of the mine that destroyed his first and only command, H.M. Submarine Tornado, now defuses ‘the beast’ on land and teaches the same deadly science to others who too often die in the attempt.