Uncle Petros is a family joke. An ageing recluse, he lives alone in a suburb of Athens, playing the odd game of chess and tending to his garden. If you didn't know better, you'd surely think he was one of life's failures.

But his young nephew suspects otherwise. For Uncle Petros, he soon discovers, was once a celebrated mathematician. A mathematician brilliant and foolhardy enough to stake everything on solving a problem that has defied all attempts at proof for nearly three centuries - Goldbach's Conjecture.