Erin Herondale & Sarah Lightwood. Jace Herondale & Alec Lightwood. Two pairs of parabatai in New York. But these four Shadowhunters aren't your regular parabatai. Not anymore, anyway. Not after their run-in with a time demon. When a bad run-in with a time demon in New York sends Erin, Sarah, Alec, and Jace back in time, the four Shadowhunters find themselves living out a story Erin and Sarah know only too well - the Infernal Devices. There's one minor problem in the arrival in Victorian London - Erin and Sarah ended up with Tessa in the Dark House, while Alec and Jace ended up in the London Institute, with no idea what's going on on, left only to hope that they're in the time of the Infernal Devices book their sisters have read and that the girls will show up. But are the boys ready for another great adventure, right after Valentine?