With ‘Dallas Buyers Club’ and ‘Wild’, Montreal filmmaker Jean-Marc Vallée has been on a hot streak of movie-star led character studies that conceal their crowd-pleasing, feel-good nature just long enough to feel like art films for a while. His latest movie ‘Demolition’ is very much in that mold, teaming up with Jake Gyllenhaal to deliver an exploration of grief that feels wildly unpredictable and darkly funny until it transforms into something traditionally sentimental just in time to send the audience out the door.

Gyllenhaal stars as Davis Mitchell, a successful investment banker who seems numbed out by his seemingly perfect life (or at least the image of one that he sought). Unfortunately, almost as soon as we’re introduced to the character, his beautiful wife is killed in a car crash. At first, Davis barely seems to react to the tragedy, showing up to work like nothing’s wrong and hardly registering emotions on his face. Then he starts writing oddly confessional notes to the manufacturer of a malfunctioning vending machine that was at the hospital where his wife died.

Soon, he starts obsessively and meticulously smashing and dismantling things in search of purpose. A self-destructive streak kicks off in him around the same time that he starts literally destroying things (metaphor alert!). The woman who has been receiving his letters at the vending machine factory (Naomi Watts) begins phoning and following him, obsessed with his odd behavior. He hangs out with her and her son, in between rounds of smashing things and burning bridges with his ex-wife’s family as well as everything else from his former life.

If you know anything about the stages of grief, you can probably tell where this is headed and it’s just as squishy, soft and sentimental as you’d fear. However, the film is actually quite good until stumbling into its prescribed finale. Gyllenhaal is excellent as an unhinged man in a wildly unstable manic state. The movie is as darkly comedic and unpredictable as the character during the bulk of its running time, which is pretty fascinating to watch. Gyllenhall, Watts, Chris Cooper (as the father-in-law), and Judah Lews (as Watts’ son) all play their broken humans with a mixture of warm empathy and dark wit that can be quite impressive.

It’s a shame that Vallée and Gyllenhaal weren’t able to find a way to end their story in the midst of the protagonist’s mania. Once he comes crashing down from that wide-eyed wild high, the story grows increasing sentimental and predictable. Vallée seems to realize it too, rushing through the finale in a series of dialogue-free montages hoping that reducing those rote scenes to pure imagery will somehow make them more interesting. It doesn’t quite work and it’s sad to see such a weird, dark and fun movie dissipate into such a tiresome depiction of grief. ‘Demolition’ isn’t a terrible movie, but it’s definitely a wasted opportunity.