Seven years ago, Maeve Abanthee lost everything when her father was accused of killing an entire world-and everyone in it. Now eighteen, Maeve lives under an assumed name, doing her best to leave the past behind. But when she receives an anonymous letter claiming that her father is innocent, she finds that letting go of the past isn't as easy as she expected.
Hoping to learn more about her father and the mysterious letter, Maeve infiltrates the Otherwhere Post, where couriers use the magic of scriptomancy to deliver letters across the boundaries of worlds. She intends to keep to herself, staying only long enough to find answers, but when she's assigned to train under a dark-eyed boy who sees through her lies, things become more complicated than she expected. As she digs into the past, she begins to unearth a deadly conspiracy-and as threatening notes appear in her satchel, warning her to drop the investigation, she realizes that she may be the next target.