A game of lies by Clare Mackintosh

"They say the camera never lies. But on this show, you can't trust anything you see.
Stranded in the Welsh mountains, seven reality show contestants have no idea what they've signed up for.
Each of these strangers has a secret. If another player can guess the truth, they won't just be eliminated - they'll be exposed live on air. The stakes are higher than they'd ever imagined, and they're trapped.
The disappearance of a contestant wasn't supposed to be part of the drama. Detective Ffion Morgan has to put aside what she's watched on screen, and find out who these people really are - knowing she can't trust any of them.
And when a murderer strikes, Ffion knows every one of her suspects has an alibi . . . and a secret worth killing for."