Luke and Luna have moved on since Waverly, this time making their way to South Dakota to train the grumpiest part Guardian and his cheerful sister. While Jasper and Lenai are being trained, other things just have to get in the way: Hunter attacks, huge misunderstandings, and, of course, kidnappings. But there's a bigger distraction: a third Guardian, and he's not exactly the friendly type. Despite his secrets, Luke and Luna are determined to get him to trust them, while hoping that it's not going to be a mistake.