A respected organization, a hidden purpose, a world-ending threat. 12-year-old Maggie Thatcher longs to be a courageous Wayfinder Girl. But that's not very likely; she is barely coping with life as it is, relying on her asthma inhaler, epi-pen, and the support of her best friend, Anahira Waititi. Maggie and Anahira attend a Wayfinder 'apocalypse training' camp in London. Despite it being just for fun, the sight of a green-skinned person with other-worldly eyes sends Maggie into a panic, especially as it's a person that only Maggie can see. And then Maggie learns of a dangerous secret that the Wayfinder Girls have kept hidden from the world. Anahira wants in on the secret. Maggie must decide whether to join her friend, even if she has no idea what that decision will ultimately cost. Will Maggie face her fears and journey into the unknown? A Wayfinder Girls adventure filled with mystery, magic, and mayhem.