The moonlit door - Deryn Lake

A new puzzle for the Reverend Nick Lawrence . . .
It is May in the sleepy village of Lakehurst, Sussex, and Nick Lawrence has organised a Medieval Fair, complete with maypole dancing, archers and Mr Grimm's men, a group of Morris dancers. The fair is enjoyed by all and a great success, but once the village green is deserted a horrific event takes place that shocks the whole village. A young orphan, Billy, is shot through the heart with an arrow and his body covered with the ribbons from the maypole.It is up to Nick and Detective Inspector Dominic Tennant to try and find out who would commit such a horrific crime - and why?