Stunning location work and two performances of considerable force distinguish Belgian director Fabrice Du Welz’s English-language second feature. It’s a dark and pessimistic drama which goes slap-happily mad towards the end but keeps you watching all the same.

Emmanuelle Béart and Rufus Sewell play the protagonists — a couple devastated by the loss of their son in the 2005 tsunami but, since the body was never found, hoping against hope that he is alive. The wife, in particular, refuses to believe he is dead, especially when she watches a video of boys kidnapped by traffickers in the chaos that followed the catastrophe.

The pair have remained in Phuket where she persuades her sceptical husband to pay first a local petty crook and then a sinister boatman to take them into the pirate-infested no-man’s-land of the Thai-Burmese border. It is permanently raining and the jungle is dangerous. Each step they take into the unknown necessitates another dollop of money for their guides.

Benoît Debie shoots the scene brilliantly and both the increasingly desperate wife and the desolately cynical husband are portrayed with terrifying realism. The boys they find huddled under makeshift shelters are, of course, not theirs. “Does it matter?” says their guide when one of them stretches out his arms to Béart, who instantly rejects him. “It’s a child, isn’t it?”

What then happens pitches the film into a nightmare that in the end destroys the real horror of the story. There can be nothing but praise for the performances of both Béart and Sewell, and Du Welz is clearly a talented director — but his attempt to engineer a ghostly, supernatural ending pushes his movie into the realms of arrant melodrama.