After discovering an alchemic image purposefully left at the crime scene, denoting the first of four stages of a process called 'Magnum Opus', the team realise that there are three more murders to follow.
When an idyllic Oxford summer's day is torn asunder by a gruesome parcel bomb, Lewis and Hathaway are called to investigate. The victim of the attack is an eminent mathematician, a genius in the field of 'Knot Theory.
Lewis and Hathaway investigate the death of Reuben Beatty, a research fellow from the University of Oxford’s Department of Psychology. He is found dead - injected by etorphine, a powerful paralysing agent.