Girl In The Woods by Jennifer McMahon
Close friends Henry, Tess, Winnie and Suz spend the summer after graduation in a remote cabin in the Vermont woods where they play elaborate, sometimes dangerous, games. But everything changes when one particularly twisted experiment ends in Suz's death, which the others decide to cover up. Nearly a decade later, Henry and Tess are married and living an hour's drive from the old cabin. Though they have tried to forget that summer, the past isn't ready to let them go. When a victim of one of their past pranks commits suicide - seemingly triggered by a mysterious postcard - it sets off a chain of disturbing events that threatens to engulf them. Is there someone who wants to reveal their secrets? Or is it possible Suz did not really die?