It’s difficult to think the worst of a character who looks like the Mexican actor Gael García Bernal. We instinctively warm to the gauche boyishness and the engagingly crooked smile. The ruthlessly effective shock tactic that the director James Marsh employs in The King is to cast Bernal as Elvis, an amoral sociopath with the destructive potential of an Exocet missile. Elvis has recently been honourably discharged from the Navy. His plan is to return to his home town of Corpus Christi, Texas (the choice of town name is no accident), and seek out the father he has never met. David Sandow (William Hurt) has forged a new life for himself as a respected local Baptist pastor with a God-fearing family and a comfortable suburban home. He’s not about to welcome an illegitimate, half-Mexican son into the fold.

Elvis is a Ripley-like character whose talent is to identify a way in to the family, which is more vulnerable to his charm assault. Sixteen-year-old Malerie (Pell James) has no idea that she shares DNA with her new friend as well as stolen moments in his beaten-up car.

The film, a slow-burning Southern gothic, steeped in dysfunction and religious fundamentalism, is a tricky beast for the reviewer. Both its strengths and weakness are inextricably enmeshed with crucial plot points about which, ideally, the potential audience should know nothing. Elvis is an enigma throughout the film, but Bernal is sufficiently skilled to balance this moral ambiguity with a darker strand of real menace.

Still, we’re left with more questions than answers — is the chaos premeditated or is Elvis a delusional loose cannon who believes his own tall tales? Is his intention to insinuate his way into the family like a cuckoo in a nest, or does he just seek to destroy the nest entirely? Malerie is a more problematic creation, largely because of James’s wan and insipid performance. Her domineering Daddy may have left her unprepared to stand up for herself, but even so, her perpetual state of bland indifference just doesn’t ring true.

Marsh examines the hypocrisy of modern religious fundamentalism but does so by borrowing themes from the Old Testament and Greek mythology. The result is a curious tone — suffocating domesticity tempered by sudden stabs of baroque violence. There are too many questions left for this to be an entirely satisfying experience, but it’s certainly an intriguing one.

WENDY IDE

Explore Film

• Film Reviews

• Trailers

• DVD

• London Film Festival

Editor's choice

• The 100 Best Films of the Decade
• 70 facts you didn't know about Marvel
• The 50 Biggest Movies Of 2010