Maria (Elena Anaya) suffers every parent's worst nightmare as her young son Diego disappears during a ferry trip to the holiday island of El Hierro. She returns some time later to identify the body of a child washed up on the shore, yet it is not her son.
After a chance sighting of a boy on a beach, she sets off to find out whether Diego may still be alive, confronting the darker side of the island while attempting to hold on to her sanity. Hierro is sumptuously directed by Gabe Ibáñez in his feature debut, and Anaya carries the film with a strong performance. But it struggles with pacing and culminates in an ending most will have guessed halfway through.