Florence, October 1966. The rain is never-ending. When a young boy vanishes on his way home from school the police fear the worst, and Inspector Bordelli begins an increasingly desperate investigation.

Then the flood hits. During the night of 4th November the swollen River Arno, already lapping the arches of the Ponte Vecchio, breaks its banks and overwhelms the city. Streets become rushing torrents, the force of the water sweeping away cars and trees, doors, shutters and anything else in its wake.

In the aftermath of this unimaginable tragedy the mystery of the child's disappearance seems destined to go unsolved. But obstinate as ever, Bordelli is not prepared to give up.