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 first, contained groups of people, young and old, and suddenly it’s a plague – and ten days later it’s killing people. The hospitals are overflowing and there is no cure. There is a paranoid panic which sets friend against friend, neighbour against neighbour. Where does the world go from here? In the north London school where it is first discovered, head of English, Kit Chaplin is struggling to understand what he is witnessing. Even eminent bacteriologist and his partner Lilly Slater can’t help him. But as the virus rips through the school and into the outside world, the world starts to take notice.