The town says he drowned. Every night, she knows better. Six months ago, on the night of the worst storm the town could remember, Tom walked out into the rain and never came back. By morning a boat was missing from the harbor. Everyone agreed on what that meant. Everyone except his wife. Kate is a nurse. She knows what death looks like, and this is not it. Tom left his pajamas folded on the pillow. He left thirty-one books about dreaming on his shelves, and a promise, made that same evening, to take her with him wherever he was going. Since that night she has dreamed the same dream: a ruined city under a gray sky, a single oak tree, and silent figures in the rubble who seem to be waiting for her to understand. Then, one night, the dream gives her a road. It leads to the In-Between Hotel, headquarters of the agency that polices every world a sleeper can enter. Its rulebook is a thousand years old. Its agents are courteous, efficient, and immovable, and they have one piece of advice for a widow with no license and a key that belongs on no list: go home. Kate is not going home. Beyond the last of the guarded worlds, a man is erasing entire civilizations one by one. The last person seen at his side was her husband. To dream is to resist.