Who let the gods out?

Twelve-year-old Elliot Hooper has many problems: his mother has been behaving strangely, they are in danger of losing their farm to a mean-spirited developer, and he is failing at school, so when he finds a girl in the cowshed, and she announces that she is Virgo, an immortal constellation, it just seems part of the normal chaos--but soon he is swept up in the Gods' hunt for prisoner 42, Thanatos, Daemon of Death, whom Elliot has set free from his prison below Stonehenge.