As The Shell House Detectives try to solve a family mystery, their investigation runs dangerously close to a murder case. Are the two linked?

It's December in Cornwall, and Mousehole harbour is illuminated with its famous Christmas lights. Ally Bright is among the crowd listening to the carol singers--and then to the piercing screams that rip through the darkness. A body has been found, brutally murdered and dumped in a fisherman's boat.

The victim is chef JP Sharpe and there is no shortage of people who might have wanted him dead. Eager for a new case for The Shell House Detectives, Ally calls ex-cop Jayden, but he's keen to leave it to the police--until a letter in Sharpe's pocket draws them into a seemingly unconnected family mystery. As they take on this highly charged mission, the duo can't help scrutinising the murder suspects. Who among the close-knit community has reason to kill, and how far will they go to protect themselves?

As fear spreads, Ally and Jayden need answers--fast. Could the letter offer a clue to the murder case or will it reveal a terrible truth? And when a new witness comes to light, Jayden closes in on a desperate killer...but can he warn Ally in time?