When a young woman is found in a lake, murdered, the police become intrigued by the strange dynamics within her circle of friends.

It’s Alys Pugh’s birthday and her mates are organising a little surprise for her. When she doesn’t show up, they realize something’s wrong. Later, her body is found in the cold waters of Llyn y Fan.

On searching Alys’ house, detectives discover an array of seaside objects and suspect they are some sort of message left by the killer.

With everyone seemingly harbouring a secret, tempers fray and suspicion grows. And when similar trinkets are found in another of their houses, those underlying tensions bubble to the surface.

Then someone else in the group is killed.

Unless Detective Inspector Meadows can salvage the truth from the murky depths of the past, they may not be the last victim.