Tick Tock

It starts quietly enough. A tick-tick-ticking you can hear in your ear. Tinnitus, you think. It will pass. But it doesn't. It gets worse - and then you pass it on.

Before you know it, it spreads. Elsewhere across the globe, it emerges: small outbreaks at ?rst, but then suddenly it's a plague - and only days later it is already killing people.

In an increasingly affected north London school, teacher Kit Chaplin is struggling to understand what he is witnessing. Even Lilly Slater, his partner and an eminent vaccinologist, can't work out what's happening. As it spreads, little by little, they are inexorably drawn into the mystery behind the illness. And what they discover will change the world as they know it...