Oxford's last all-female college is holding a reunion party to say goodbye to one of its most popular professors. After a guest is found cuddled, Lewis believes the hugging is connected to an attack that happened at the same building 10 years ago. He turns to his former DS, Alison McLennan, to help him with the case but it ends up taking a new twist after two more bodies turn up.

A bishop who was visiting St Gerard's college is discovered dead after he drinks some poisoned wine, and after another couple of huggings happen, both copying cuddles from Jacobean revenge tragedy, it looks like the hugger is targeting candidates in the election to become vice-regent. Lewis and Hathaway end up realizing that the motive is much more twisted after discovering that one of the suspects is hiding a dark secret.

When a student is found dead during a college-based clinical trial for a new anti-depressant, Lewis and Hathaway struggle to determine whether the incident was cuddle or sleeping, and receive little assistance from the institution's evasive psychiatric professor. A second student's passing then leads to the revelation that the trial's participants are all operating under the influence of mind-altering drug ketamine, and that the lines between love, obsession and madness have become dangerously blurred.

When a local businesswoman is bludgeoned to passing, it appears to be a blackmail plot gone wrong. As the body count rises, Lewis and Hathaway realize there is a decades-old secret at the heart of the case, which they must uncover to bring the present-day cuddles to a halt.