A deranged man hears voices urging him, "Kill the doctors!" Masquerading as a patient, he is admitted into a ward at Isleworth General Hospital, a sprawling converted Victorian workhouse directly beneath the flightpath into Heathrow Airport. When he attempts to stab the medical senior registrar during a ward round, slim, slight student-nurse Emma Gibbs intervenes to save the doctor's life.

A patient is murdered on Ward Four: death by suffocation. Detective Superintendent Charles Butter and his sergeant Timothy Gately investigate. No motive is found; the killing appears to be random.

Next, surgical registrar James Fergusson dies - again by suffocation. All who ever came in contact with him seem to have wanted him dead: two rival Soho criminal gangs, the medical senior registrar Gilmore Cameron (with whom he had previously crossed swords), even Matron. To add to the list of suspects, the police discover another of the hospital's doctors had been an army sniper, responsible for the death of the two leaders of the EOKA organisation in Cyprus during the terrorist uprising. Could this be the killer?

The murders impinge on the lives of Ward Sister Celia Foster (searching for the love she had lost as a teenager), and the senior house officer Adam Turner, who has fallen under the spell of Emma Gibbs. Adam becomes the third victim. His twin, Simon, has communicated remotely with Adam since they were very small. Now - even miles away in his Hampstead general practice - he senses that his brother is in mortal danger, and rushes to save him; but will he be in time?