A darkly humorous rumination about the primacy of fate or free will presented in the form of a twisty thriller with a smidgen of the supernatural, Dru Brown’s “The Suicide Theory” is good enough to bear comparison to the Coen brothers’ “Blood Simple” or Christopher Nolan’s “Memento.” Even if in the final analysis the Australian import falls a bit short of either, it’s well worth investigating.

In what’s basically a two-character piece, Steve Mouzakis stars as Steven Ray, a stone-cold, natural-born contract killer on the job in Brisbane who, in an opening scene, happily bashes in the head of a man he’s never met before simply because the fellow has casually disrespected him. Though he’s being pressured by his boss to complete his current assignment, he’s hobbled by trauma caused by the recent death of his girlfriend in a hit-and-run just outside the opera house he regularly frequents—a condition that leads him to wear her clothes on occasion and leaves him with a psychological block against crossing streets for fear of reliving the accident.

One night while he’s arguing with a cab driver, a body falls on the hood of the car. It’s Percival (Leon Cain), who’s trying, not for the first time, to commit suicide—the result, we eventually learn, of grief over the death of his lover. But all his attempts have been unsuccessful, so he hires Steven to do what he’s literally unable to himself however hard he tries. It’s a curse, he explains: every time he attempts suicide, he awakens in the hospital with a doctor giving him the dismal news that he’s exceedingly lucky still to be alive. Steven doesn’t believe Percival, but is soon convinced when the man survives even his well-placed bullets. Percival urges him to keep on trying, but adds that he’ll be able to succeed only if he attacks at a time when Percival doesn’t want to die.

One might object at this point that Steven seems unlikely ever to succeed, given the extent of Percival’s depression. But he’s a bulldog in more than facial expression, and undertakes to get his target into a life-affirming state so he’ll be able to kill him. In the process the two develop a weird friendship despite their differences, and Steven even becomes protective of his new buddy/client. Further details about how the labyrinthine plot proceeds will not be revealed here; to do so would spoil the fun.

The script by Michael J. Kospiah lays out its tricks cleverly, using some chronological juggling and abrupt shifts from character to character to keep the viewer slightly off-kilter, generating considerable black comedy from the resignation of Percival in the aftermath of each of the attempts on his life, and tying all the threads together in an ending fraught with coincidence that embraces one of the alternatives in the fate-free will debate without demur; editor Ahmad Malini’s contribution is important in keeping the screenplay’s swerves clear while maintaining their mystery.

Of equal importance are Brown’s canny direction, Dan Macarthur’s noirish cinematography, and the lead performances. Cain exudes bedraggled desperation as the wannabe corpse, but it’s Mouzakis who carries the film with a turn that wouldn’t be out of place in one of Scorsese’s gangster epics or a season of “The Sopranos.” By turns terrifying, pathetic and gregarious, he fully fleshes out a role that might have been static and stereotypical.

As “The Suicide Theory” grows increasingly convoluted, especially in the last fifteen minutes when it springs its most outrageous surprises, some viewers may find themselves losing their ability to suspend disbelief. But the puzzle Kospiah and Brown have fashioned does come together in a coherent whole, and even if you don’t buy into the conclusion about the balance between destiny and free choice it posits, you should still enjoy having taken the trip to the end. Like films as varied as Shyamalan’s good ones (“The Sixth Sense” and “Unbreakable”), Bryan Singer’s “The Usual Suspects” or the underrated Anthony Perkins-Stephen Sondheim collaboration “The Last of Sheila,” it will make you smile however ridiculous you find the solution.

It’s always nice to encounter a little film that can be mentioned in such company.