A Shadowhunter allying with a demon is unspeakable. So what happens when a Shadowhunter makes a contract with a demon? Collateral damage. Universal threats to Mundanes, Shadowhunters, and Demons, and Downworlders alike. The Phantomhive household and the London Institute will need to work together to reclaim one of their own kind to the light… or eliminate him completely.

Vincent has a request, and Frances has never been one to refuse her brother when he has a job for her. This one turns out to be just the slightest bit unexpected. Crossover with Cassandra Clare's The Infernal Devices. Set a year before Clockwork Angel. Oneshot.