An experimental vaccine is stolen, and the subsequent test proves deadly. Steed and Keel, suspecting that the human 'guinea pig' did not die directly from the vaccine, volunteer to be the next subjects.

When an agent is killed in the lift of Pinter's Department store, Steed and Emma get involved with King Kane, a tycoon who lives in a penthouse above the store. Why is Professor Popple, a missing atomic scientist, being held in the bargain basement?

A European peace conference comes under the threat of sabotage when the British delegates begin to suffer from premonitions and nightmares. After Sir Andrew Boyd, who has witnessd his death in a dream, is killed, Steed and Emma must keep his replacement, Lord Melford, sane and alive.