She Lies In Wait by Gytha Lodge

Seven teenagers went down to the woods. Only six came back . . .

30 years later, a body is discovered. DCI Sheens already knows what's waiting for him - Aurora Jackson, found at last. What he doesn't already know is that it's murder.

All six witnesses insist on their innocence, but DCI Sheens is sure one of them is lying. But who?
 
'What a marvel! A corkscrew-twisty, knife-sharp thriller. . . Prepare to be haunted' A J FINN, bestselling author of The Woman in the Window