On his ninth birthday, the extraordinarily accident prone little oddball Louis Drax (Aiden Longworth), who has already survived eight brushes with death, tumbles off a cliff into the ocean. As he lies comatose, neurologist Dr. Pascal (Jamie Dornan) attempts to reach the boy and a police investigation led by an inscrutable detective (Molly Parker) probes Louis' short, troubling life and the disappearance of his father Peter (Aaron Paul). Meanwhile, inside Louis' supposedly persistent vegetative state the boy is guided through a dreamscape of memories, fears and sorrows by a persistent but protective sea monster who urges him on the dark journey to the truth.

Max Minghella's screenplay adaptation of the novel by Liz Jensen is intelligent and sensitive, negotiating the mystery, suspense and supernatural fantasy elements in a story that is grimly realistic at its sad heart. French director Alexandre Aja has, since his The Hills Have Eyes re-make, striven somewhat in vain to put his own stamp on fantasy horror like Guillermo Del Toro. As he did in the long-shelved Horns – and Louis Drax, too, has languished for many months since being made – Aja wrestles with tone.

Pretty underwater scenes and aerial shots of San Francisco rising out of low clouds lay it on thick that this is an under the sea / above the clouds fairy tale, and there are a couple of creepy flourishes, but scenes of police interrogations and sessions with the boy's kindly shrink (Oliver Platt) are like every TV procedural. And while it may be novel to see Dornan mostly fully clothed, Dr. Pascal is, for an acclaimed medical scientist, awfully dumb.

Kudos, then, to Aaron Paul for the most heartrendingly believable and sympathetic performance in a decent ensemble, especially if that really is him swathed like a mummy in dripping seaweed in one memorable scene.

Key cities from Fri 2 Sept.