Paul Zindel - The Doom Stone

Synopsis:
A killer beast half-man, half-apelike terrorizes the English plain on which Stonehenge lies. Fifteen-year-old 
Jackson Cauley, with the help of his anthropologist aunt and a local girl, has tracked down the 
predators lair. But the source of the beasts power lies in the ancient Doom Stone of Stonehenge, 
and unless its secret is unlocked, the deadly slaughter will continue.