Two time-traveling agents from warring futures, working their way through the past, begin to exchange letters—and fall in love in this thrilling and romantic book from award-winning authors Amal El-Mohtar and Max Gladstone. Among the ashes of a dying world, an agent of the Commandant finds a letter. It reads: Burn before reading. Thus begins an unlikely correspondence between two rival agents hellbent on securing the best possible future for their warring factions. Now, what began as a taunt, a battlefield boast, grows into something more. Something epic. Something romantic.