Sometimes the truth lies in the things you cannot see. In 1830 a young novice called Catherine Labouré was granted a vision of the Virgin Mary. Nearly 200 years later, Sister Anne is also waiting for a sign.

Which is why she accepts a mission to go to a tiny community on an island just off the coast of Brittany. Her only companion there is a sceptical, chain-smoking older nun who just wants to be left in peace. On the island she meets Hugo, the son of a devout family who prefers to look for the meaning of life amid the stars; Madenn, a grandmother whose daughter was killed in a crash and who finds meaning in routine; Isaac, Madenn's grandson, an otherworldly teenager who doesn't fit in but who befriends Hugo, and Julia, a sickly child.

If anyone needs a miracle, it is her. But it is not Sister Anne who receives a vision. Instead it is Isaac who is found on a promontary, transfixed, unable to utter more than the words 'I see'.

The event soon becomes headline news and the world descends on the small island, opening old wounds and unleashing a chain of events none of them could have foreseen.