Dave Wong (Daniel Wu) is not the most popular officer on the Hong Kong police force: although dedicated to his job, he has an aloof manner that does not endear him to his colleagues and has resulted in various transfers throughout his career, with ‘personality issues’ standing in the way of promotion despite an otherwise solid record. Admitting that he chose to become an officer of the law because wearing the uniform makes him feel safe, Wong spends most of his free time hiding away from the world in his tenement apartment with visits to his grandmother (Fung So-bor) constituting his only significant personal relationship. However, as he’s a protagonist in a typically hectic Dante Lam thriller, it will not be possible for Wong’s life to remain sedate for long. While stationed at a hospital, he donates blood to save the life of injured criminal Hon Kong (Nick Cheung), a freelance operator and cop killer who has just participated in a robbery with the notorious Demon King Gang. Wong later experiences overwhelming feelings of guilt when the recovered Kong escapes from custody. Setting out to bring Kong to justice by any means necessary, Wong unravels psychologically as he confronts his fears head-on.
The none-too-subtle title of That Demon Within works on two levels as there is a suggestion that the straight-laced Wong has been possessed by the evil spirit of Kong since his behavior becomes increasingly erratic and he eventually goes to Machiavellian lengths to turn the Demon King Gang against one another, but he is also driven by a barely-repressed childhood trauma that is not fully explained until just before the end credits. Wu, a dependable leading man who has rarely been pushed to the dramatic limit, is clearly keen to prove that he is capable of greater depth and looks credibly withdrawn throughout but Lam’s increasing reliance on hallucinations for shock effect at times reduces his committed performance to a series of pained reaction shots. Cheung makes the most of his one-note role as Wong’s extremely nasty adversary, but is off-screen for long stretches meaning that the intended yin and yang effect is never fully realized. With the villain left to grin wickedly on the sidelines while the hero tries to get to the root of his mental disturbances with assistance from therapist Stephanie (Astrid Chan), the mid-section flags severely despite Lam’s efforts to keep Kong in play by featuring him prominently in Wong’s nightmares.
Lam’s reputation as a smart commercial filmmaker with a flair for slick crime thrillers was cemented by such hits as Beast Stalker (2008) and The Stool Pigeon (2010), with his rousing MMA drama Unbeatable (2013) representing a nicely judged change of pace. His growing status presumably earned That Demon Within its slot at the Berlin Film Festival and recent limited US theatrical run, but this is one of the director’s weaker efforts as he struggles to fuse police procedural and supernatural horror. Shooting around the streets and dilapidated housing estates of Kowloon, Lam and cinematographer Kenny Tse work hard to paint Hong Kong as a hellish urban landscape that sucks even noble-minded law enforcers like Wong into its abyss. However, the crisp digital photography prevents this aesthetic from capturing the requisite grime, while an abundance of cheap CGI makes the sporadic shoot-outs – which feature gunshot victims flailing around on the ground with limbs missing and an abundance of fireballs– feel garishly cartoonish. Lam mines some mordant humor and clever symbolism via the Demon King Gang who all have day jobs in the funeral industry and wear traditional masks when committing robberies, but That Demon Within is a largely overwrought affair that loses interest long before its climactic conflagration.