Atomic Coffin - Benedict Anning

December 1984. SIS field asset Heidi Sperling [codename Thistle] exfiltrates from East Berlin with the sole copy of a critical intelligence leak: a naval log containing a solitary message received from a previously unidentified Soviet submarine.

Incredulously impossibly it seems the vessel, known only as TK-15, has been sitting motionless and undetected in the waters between Scotland and Iceland for three whole years. And now this latest message reads: ACTIVE.

Picked up by the Royal Navy s submarine HMS Viking, Heidi is thrust into a 'black ops' mission: find TK15 and neutralise it at any cost. But as her only ally on board the Viking falls sick, she realises this modified vessel is far more than a Soviet experiment to gain an upper hand in the nuclear arms race. Here, in the crushing depths of the North Atlantic, it seems something darker has awoken - something that cannot be contained by any superpower.

As Heidi s own reality twists around her, an unknowable force cripples the Viking's defences and drives its crew to madness. Trapped in the deep, Heidi has no choice but to find a way to save the remaining crew and stop TK-15 for good, before it steals what s left of her mind . . .