"Off With His Head" by Ngaio Marsh 1958

Synopsis from the web
On each Sword Wednesday, that nearest the winter solstice, the inhabitants of the two remote villages of High and Low Mardian gather for a dance. The climax of this is a sword dance in which the Five Sonse cut off the head of their father, the Fool in a sort of mime in which the blood is provided by a rabbit's head; the Fool then hides for a time, to reappear at the end, resurrected. The dancers this year - and, indeed, every recent year - are really a father and his five sons; and this year the father is really killed.

"...all in all, Off With His Head is one of Marsh's worst novels"