After a tough end to the school year, the Math Kids—Jordan, Justin, Stephanie, and Catherine—take a jet to London for an exciting summer vacation. But between exploring the city and seeing the sights, they’re quickly drawn into investigations of terrorist activity. Authorities are on high alert because of threats to landmarks across the city. But there’s something odd about the messages. Working alongside Bobby, a police officer tasked with being their trip guide, the kids must uncover the true purpose of a mysterious online message board or risk being sent home early. With their vacation plans and the safety of London at risk, the Math Kids are in for their most complex case yet!