Three boys, two grandpas, a tree, a map and some hidden treasure... Let the adventure begin.

Eleven-year-old Nicholas Funes knows he's weird. He plays the violin far too well to be cool, he collects square roots and prime numbers and, weirdest of all, he talks to a tree who he believes is his brother. Plus, he doesn't have all that many friends. But even he is about to struggle with how strange his life is about to get. His long-lost and never-spoken-about Grandfather Rose turns up on Nicholas's doorstep one day, fresh out of a lifetime's prison sentence and suffering from dementia.

Curious about this grandfather he's never known, Nicholas tries to unravel Grandfather Rose's stories. In particular, one about the family treasure that he hid years ago and that will be the solution to all their rather pressing financial woes. Because his mother needs to sell their house, and if they leave the house, they'll leave Nicholas's brother behind. And Nicholas is desperate to keep what little family he has together. With the help of two extremely unlikely allies, Nicholas must unwrap the secrets of his family's past in order to give them a shot at a future.