In the companion to Under Their Skin, Haddix does what she does best: tells an engrossing story and raises important questions. With plenty of material begging to be discussed, this conclusion to the 2-book series will engage young adult readers, even reluctant ones. Twelve-year-old twins Nick and Eryn and their robot stepsiblings, Jackson and Ava, try to save humanity from killer robots.

Nick and Eryn must figure out a way to save the world without sacrificing their newly discovered family in this follow-up to Under Their Skin, which Booklist called “crisp, intriguing, and thought-provoking” in a starred review.

In Under Their Skin, twins Nick and Eryn successfully met their new stepsiblings, Ava and Jackson. But in doing so, the twins found themselves on a mission to discover how to prevent humanity from facing certain doom.

Now, their two families are joined together to save not only themselves, but everyone—human and robotic. Can they figure out how before it’s too late?