The Box In The Woods by Maureen Johnson

A teen sleuth is invited to a once-notorious summer camp to reexamine the unsolved 1978 murders of four counselors, but the cold case turns hot when new threats—and then a new killing—suggest the original murderer may still be at large; with her friends’ help, she navigates small-town grudges, buried secrets, and red herrings to uncover the truth hidden in the trees.

Purchase from Bookshop.org