The Doom Stone — Paul Zindel

IT'S NOT HUMAN--AND IT'S AFTER HIM!
Jackson is always eager to visit his aunt Sarah at her anthropological digs. This time she's in England, at Stonehenge, and Jackson's particularly, excited to see the massive and mysterious stone formations in person. But then he sees a young man viciously attacked and witnesses a similar savage attack on his beloved aunt Sarah. A beast no one has ever seen before is on the prowl. Jackson must rush to stop the beast before it can kill again and to save his aunt from a debilitating mind-meld with the creature. This leads him to Stonehenge, where he and his new friend, Alma, the gravedigger's daughter, risk their lives to solve the mystery of the inhuman monster that is stalking the countryside -- before it's too late.