After twelve-year-old John Boarhog's mom dies, he refuses to be schlepped off to the Jersey Home for Boys, where kids are forced to make skinny jeans for hipsters and are fed nothing but kale. Instead, he makes himself a snug home in the ceiling of the New York Museum of Natural History, where he reads anything he can get his hands on and explores the artifacts after-hours.

But when a rare Egyptian ruby--the highlight of the museum's new exhibit--goes missing, John is accused of the crime. That is until the unpredictable Inspector Toadius McGee sweeps in to wrestle control of the case, certain that the true culprit is a notorious criminal he's been tracking for years.

John quickly becomes the Watson to Toadius's Holmes as they race from Broadway to back alleys to a speak-easy that only serves root beer. And along the way, John uncovers secrets about his own past, including that he's a lot more involved in this web of endearing ne'er-do-wells than he ever could have imagined.