You cannot change fate.Cassandra Wright is a Timewalker - a teenager with a genetic mutation that allows her to manipulate the flow of time. But her inexplicable powers have made her a target for Adjusters - monstrous assassins from a parallel universe. Saved from almost certain death, Cassie is pulled into a secret agency sworn to defend our timeline against these threats: the Bureau of Temporal Integrity, Monitoring, and Execution. Cassie's life soon becomes entwined with Shaun Briars - a reckless Timewalker with an alluring smile and dark suspicions about the Bureau itself. When Cassie and Shaun cross into the parallel universe, they discover a world in the grips of nuclear winter, with a new war threatening to spill over into our universe. With time running out, they must learn the true history of Timewalkers, confront the unforgivable crimes of their future selves, and defy their own fate to save two worlds.