Tony Massini died when Gabriel dusted a concert audience with botulism toxin. The poisoning killed dozens of people and devastated his best friend, Danny Murphy. Then Danny learns that Gabriel warned the city about the poisonings in a threat that included a crazy demand for money and a bacteria sample with a biohazard warning.

The news that Tony's death could have been prevented leaves Danny reeling. He becomes obsessed with revenge and hunts for Gabriel while the number of victims skyrockets and the death count soars. Botulism spreads through the city. Its source can't be found until a test of Gabriel's sample reveals that common bacteria have been modified using the CRISPR technology to produce botulism. The city is quarantined.

Gabriel sends another threat and begins poisoning the money supply. The death count jumps again. The search becomes so desperate that government reaches an uneasy truce with the scientists. Danny continues his hunt for vengeance while social upheaval upends society.

Gabriel releases his final threat: Pay me now or I'll publish the genetic code that turns any living organism into a plague. Then he publishes his secret before he can be paid. Why? If not the money, what did Gabriel really want?

New plagues appear outside the quarantine line, diseases added onto modified bacteria found in every human mouth or gut. Flesh-eating bacteria and worse horrors, spread by a touch, a kiss, or just a sigh. The quarantine line collapses, then reverses. Instead of the outside world locking the city in, the city tries to lock the world out. Danny loses hope of revenge as he loses his family, his city, his confidence in the future. Everything has changed. He has no idea who or what to blame. He isn't even sure blame matters. He just needs to find his way in a world where maps are redrawn from day to day and the needle on his moral compass spins out of control.