Sir Rudri Hopkinson, an eccentric amateur archaeologist, is determined to recreate ancient rituals at the temple of Eleusis in Greece in the hope of summoning the goddess Demeter. He gathers together a motley collection of people to assist in the experiment, including a rival scholar, a handsome but cruel photographer and a trio of mischievous children. But when one of the groups disappears, and a severed head turns up in a box of snakes, Mrs Bradley is called upon to investigate.