I Made You Up Inside My Head by Marta Pérez-Carbonell

On a sleeper train from London and Edinburgh, a woman and two strangers pass the time by telling stories about their lives. One man reveals the true story behind the novel he wrote: the young man, Hans, who trusted him with intimate details about his life, and whose confidence he betrayed when he converted Hans's life into fiction for his own gain. As her cabin-mates reveal that Hans has since disappeared, with foul-play suspected, Alicia becomes gripped by the question of what really happened between the two men. She begins to re-examine her own memories, to try and discern what brought her to this point - and her involvement in the story told that night soon goes beyond a mere observer.