The grind gets us all down sometimes, man. Doubly so if you’re trapped in a cubicle and forced to deliver phony smiles all day to coworkers you’d rather be strangling. To unwind from the grueling workday, most people will get shitfaced or hit the gym, but not Kim Byung-guk. He walks home to his Seoul apartment, sits down with his family and eats dinner. Then he takes a hammer and brutally murders them all. Someone’s got a case of the Mondays!

Hot off its midnight screening at Cannes, Hong Won-Chan’s Office had its North American premiere at the mighty Fantasia Festival. This is Hong’s first time in the director’s chair, having previously wrote brilliant films like The Chaser and the terribly under seen (in the U.S. anyway) The Yellow Sea. This time Hong sets his sights on a more contained environment that you can probably guess by the film’s title.

Both the tedious and vicious backstabbing aspects of office politics are used as a springboard for a film that teeters between an office drama and a straight-up slasher. While the screenplay gets a little garbled near the end, Office is ultimately a wickedly satisfying genre work.

After Kim murders his family, he seemingly disappears into thin air. The next morning, his coworkers are grilled by Detective Choi Jung –hoon (Park Sung-woong) and his team. One coworker in particular, meek intern Mi-rae (Ko A-sung), seems to have a connection with Kim. Her coworkers consider them “kindred spirits”, but what does that mean? Ko (Snowpiercer, The Host) shines as Mi-rae, the subservient, mousy newbie who despite her hard work, is never accepted into her coworkers inner circle.

While she begins to crumble under mounting workplace anxieties, Det. Choi’s investigation unveils a horrifying clue: after murdering his family, Kim returned to the office…and hasn’t left. Once this is revealed, Office delicately descends into psychological horror and graphic stalk and slash territory. The violence is vivid and hits hard. Hong definitely doesn’t take the less-is-more approach to his violence, which makes the spurts of blood feel less effective in parts.

Near the film’s final, nail-biting moments, Office begins to trip over its own twists. The film takes an interesting turn that adds a new layer of psycho-horror, but the logic behind this turn is a bit muddled and lacks cohesion with the rest of the film. Is it awesome to watch unfurl? Oh hell yes. If only it was balanced a bit more with the previous 100 minutes it would be more impactful and less “wha?”

This trip up near the end doesn’t take away from the previous chills – and I do mean chills. Hong displays a mastery for framing suspense. He borrows not only from the slasher genre as Kim terrorizes the office, but DP Park Yong-soo also adds a stark iciness to the proceedings. One scene in particular, where one employee things she sees someone under her desk, made my blood run cold.