Erin Herondale has grown up in London and Brisbane, away from the only family she has left - her older brother Jace. Her parents, scared to have their daughter raised by Valentine like Jace was, gave her to the Clave to look after. She was sent to London with the Greystone family until she was eleven, when she was sent to the Brisbane Institute run by the Heartson family. But Erin's fifteen now, and she's in New York, ready for the new chapter in her life. But what she doesn't know is that she'll finally meet her brother. The arrival of Erin Grace Herondale in New York is just the beginning of the Institute made of couples, siblings, cousins, and parabatai.

You know our siblings. The famous ones. Percy Jackson, Jace Herondale, Clary Fairchild, Alec and Isabelle Lightwood. they're famous. World renowned at what they do. But here's what you don't know, we've always backed them up. Every quest and every mission we've been there. Now, we're telling our story. My name is Sarah Lightwood. Her name is Erin Herondale. And his name is Jonathan Fairchild. And we, are the overlooked.

My name is Sarah Lightwood. I'm 15 years old and live in the New York Institute. Or at least I did. Then my witch of a mom made me move to Arkansas at first I was miserable. Then I was actually kinda happy. That's when I get a call from Alec. He ask me to come back and at first I say no. And then he started pleading with me so I caved. I get to the institute to see a new girl who might just bring some adventure into my almost mundane life. This could get interesting. Possible spoilers.

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?