Ngaio Marsh 
Death in Ecstasy 

Another classic Ngaio Marsh novel.Who slipped cyanide into the ceremonial wine of ecstasy at the House of the Sacred Flame? The other initiates and the High Priest claim to be above earthly passions. But Roderick Alleyn discovers that the victim had provoked lust and jealousy, and he suspects that more evil still lurks behind the Sign of the Sacred Flame…