Before buying a ticket to Premium Rush, you may want to ask yourself two rather essential questions:

1) How ridiculous is the concept of “bicycle parkour” to you?

2) Are you able to suspend your disbelief to the degree that entertainment forms like professional wrestling demand of you?

If your answers are anything other than “not at all” and “absolutely,” respectively, you may have some issues finding your way into Premium Rush, a movie that’s fun to a point and a mild chore beyond that point.

Wiley (Joseph Gordon-Levitt) is a New York City bike messenger. In this version of NYC (likely not far from the actual), bike messengers are the unsung heroes, able to traverse streets with absurd levels of skill and defiant of the police who view them as unwashed nuisances. With a smartphone in hand, Wiley can get anywhere his fast-talking boss (Aasif Mandavi) can send him, all the while gleefully trading flirtatious barbs with on-and-off girlfriend Vanessa (Dania Ramirez) and sparring with professional rival Manny (Wole Parks). When he’s called for a “premium rush” delivery, handed off by a visibly nervous and apprehensive woman, Wiley has no idea that the envelope will lead to him crossing paths with Det. Bobby Monday (Michael Shannon), a dirty cop who desperately needs the contents of the envelope, and doesn’t take kindly to Wiley keeping it on principle.

Over the course of the next two hours, Wiley plays a city-spanning game of cat-and-mouse with Monday, while an onscreen clock helps the audience keep up with the flashbacks and full circles that eventually become dizzying. It’s obvious from about ten minutes into the film that there’s a larger mystery behind the envelope, but the film doesn’t quite stick the landing. Luckily, for a thriller with twists up its sleeve, the red herrings are minimal. The story unfolds elliptically, too much so in fact, doubling back to introduce new character and side stories in the service of continually raising the stakes. This is where those pesky plot holes come in. For instance, why doesn’t Manny recognize Wiley’s enraged urgency enough to simply relinquish the envelope late in the film, rather than demanding that Wiley pursue him through an elaborate Central Park setpiece. (The film tries to explain this in a flashback, but it doesn’t hold salt.)

The questions don’t stop there. How is it that Wiley can take inhuman levels of abuse throughout the film, at the hands of Monday and cab drivers alike, only to keep pedaling? Once the secret of the envelope’s contents is revealed, how exactly will Monday be able to benefit from it? There’s a lot of nonsense going on in Premium Rush, especially in its manic third act, to the point where audiences can’t really be faulted for getting lost. While helpful, the onscreen clock ends up becoming a gimmick that kills much of the film’s momentum, assisted by the overabundance of flashbacks throughout. That said, it also sets a timetable for the incredibly impressive action sequences. From the aforementioned Central Park chase to a sequence in which Wiley has to liberate his bike from an impound lot, Premium Rush is at its best when it steps away from plot machinations long enough to capture the exhilarating speed-junkie thrills of careening between cars and existing inches away from death, which if nothing else answers the reasonable question of exactly why any of these young adults are in that particular line of work.

The film comes dangerously close to overwhelming mediocrity outside of the action sequences (and the related, impressive stunt work), but has one ace in the hole: Michael Shannon. If Gordon-Levitt delivers the sort of effortlessly charming, geekily swaggering turn he could manage in his sleep, Shannon’s embattled cop is the gleefully venomous soul of the film. Like a more controlled version of a latter-day Nicolas Cage performance, Shannon delivers his dialogue with some truly bizarre inflections, supported by the best pair of bug-out eyes in Hollywood today. As you find out how truly screwed Monday has become over the course of a single day, seemingly running afoul of NYC’s entire criminal underworld, Shannon keeps his performance tight, always knowing the exact amount of histrionics to employ while cutting an imposing, terrifying figure when necessary. For all the speed and madness that unfolds in Premium Rush, in not-quite-real-time, Shannon is the one component that’s truly memorable.