When he is invited to Sir Walter Ralegh's country estate to join the gathering of a secret society known as the School of the Night, Dr Simon Forman readily agrees. And his arrival is eagerly awaited since he will be bringing with him what is supposedly a powerful aphrodisiac, and there is no shortage of volunteers to try it out. But there are those with another use for a substance which can easily be contaminated with poison, from a young woman with a wealthy old husband, to an unknown killer intent on destroying Simon Forman. But who could hold such a poisonous grudge? One thing's for certain: Simon must find out fast before not only his reputation, but his life, is destroyed.