Twelve-year-old Hugo lives in the walls of a busy Paris train station, where his survival depends on secrets and anonymity.

But when his world suddenly interlocks with an eccentric girl and her grandfather, Hugo's undercover life, and his most precious secret, are put in jeopardy.

A cryptic drawing, a treasured notebook, a stolen key, a mechanical man, and a hidden message from Hugo's dead father form the backbone of this intricate, tender, and spellbinding mystery.