Death of a Fool — Ngaio Marsh

Someone's added a new flourish to South Mardian's annual sword dance. One of the dancers in the performance has been neatly decapitated. But was it murder... or magic? In a village so totally populated by eccentrics, anything's believable, and everyone's a suspect. Scotland Yard's Inspector Alleyn has to perform some nimble steps of his own to crack this bizarre case.