War brought the Harvest. Willa Mae Wallace is a reaper.

To support herself and her grandson Isaiah, Willa works for the blood contractor Patriot. Instituted to support the war effort, the mandatory draw-The Harvest-has led to a society segregated by blood type. Hoping to put an end to it all, Willa draws on her decades-old phlebotomy training to resurrect an obsolete collection technique, but instead uncovers an awful truth.

Patriot will do anything to protect its secret. On the run and with nowhere else to turn, Willa seeks an alliance with Lock, a notorious blood-hacker who cheats the Harvest to support the children orphaned by it. But they soon find themselves in the grasp of a new type of evil.