"We lead a quiet life. Talking to people, building up a picture. Like a jigsaw. And just like a jigsaw, we spend a lot of time sorting out pieces of sky. They may seem dull and uninteresting, but we can't leave them out."

Is a virus that takes up to eight weeks for symptoms to appear, and kills only 10% of infected people, really the perfect terrorist bioweapon?

In this sequel to The Death of a Smoker, four years have passed since Quinton Bickley-Morris, a suspected spy and adversary of the Tufton Street team, slipped out of the country undetected. After a chance sighting, Harry Nevile and his team are desperate to go after him, but the more immediate threat of a suspected terrorist attack on the government takes priority.

As Harry's team investigates, piecing together fragments of evidence, the truth is gradually revealed, and it is far closer to home than they could ever have anticipated.