(Series 2, Book 3)

The late 1960s and pirate radio is at its height.

Something stirs in the depths of the North Sea, and for Radio Crossbones that means bad news.

Lethbridge-Stewart and his newly assembled Fifth Operational Corps are called in to investigate after the pirate radio station is mysteriously taken off the air, and a nuclear submarine is lost with all hands.

Lethbridge-Stewart series 3: