Writer and director Eran Creevy’s “Welcome to the Punch” is not an unconventional action movie, but it carries out the conventions quite effectively.

This sort of film strives to raise that all-important question — who are the good guys, and who are the bad guys? “Punch” keeps audiences guessing straight through to the end, and, perhaps most interestingly, it fails to fall definitively on one side or the other.

As the opening credits play, we are placed into the center of the action as we watch a high-stakes car chase. Max Lewinsky (James McAvoy) is a London police detective in pursuit of Jacob Sternwood (Mark Strong), a man of unspecified ill repute. Sternwood is flanked by his co-conspirator, Roy Edwards (Peter Mullan). A few minutes in, the unarmed Max is closing in on the criminals when Sternwood shoots him in the leg, conveniently forging a personal vendetta between the two men.

What follows is some quick exposition describing Max’s downward spiral after getting shot. He is passed over for a promotion and becomes a mess of resentment and superiority, having to bite his tongue when he disagrees with his bosses’ decisions.

However, when the long-cold trail of Jacob Sternwood warms up, Max can’t help but get involved. He drags his partner Sarah (infused with spunk by Andrea Riseborough) into the conflict, but he refuses to take her advice on the case, instead choosing to act rashly time and time again.

“Punch” comes closest to falling apart here. After all, why should Max’s superiors allow him to be involved with the case at all when he is clearly too close to it? His single-mindedness causes far more trouble than it’s worth, especially since Sarah finds the ultimate clue far before Max is even aware that she has a lead. Sadly, McAvoy’s over-brooding personification of the character makes him petulant rather than passionate.

While McAvoy may not be perfectly suited to the action hero role, Strong is just right as the aptly named Sternwood, a solemn and strangely compassionate man with a murky past. Strong uses his considerable acting talent to pull off a characterization that is simultaneously sympathetic and apathetic. Mullan makes an excellent comrade for Strong, as an old-school partner in crime to Sternwood.

Ostensibly, “Punch” is a mostly compelling cop thriller with some nice cinematography, some good casting but some questionable plot points. What makes “Punch” interesting is that the normal “good versus evil” mold does not apply in the traditional sense. The law-abiding police officer has a tendency to be far more violent than the outlaw, but even Max is not nearly the worst of the supposed good guys. In the end, nemeses are forced to unite in the face of a force that has done significantly more harm than either of them.

Clio McConnell is a senior editor. Email her at [email protected].