Johnnie To and Wai Ka-Fai step back from the fluffy comedies and the hard-nosed thrillers to tell a story that exploits the fantastic. More like “Mad Monk” and “Heroic Trio” than “The Mission,” “Running on Karma” takes the hypothetical and makes it literal in the form of Andy Lau as the character Big. Andy once again dons a rubber suit, but this time of raging muscles. He meets up with Cecilia Cheung, playing a police officer, during a botched raid and reads her karma. Andy has the ability to see a person’s fate through that person’s past life’s transgressions. So begins the rudimentary Buddhism lesson for the day.

“Running on Karma” gives us the down and dirty on the Buddhist principle karma: “the effect of a person’s actions during the successive phases of the person’s existence, regarded as determining the person’s destiny” (The American Heritage Dictionary). The filmmakers take a philosophical point of view and present Andy Lau as an ex-monk cursed with the gift of being able to see a person’s fate, but Andy must reconcile his own mortal failings before truly comprehending what lies ahead.

Can we change fate? Are we the masters of our own destiny? Sometimes the choice has already been made for us.

Johnnie To and Wai Ka-Fai take a risk by introducing some heady Buddhist elements that could have hurt the film. They could have altered their course and made it more pedantic and mainstream, but they forge onward by not painting rosy pictures of Lau and Cheung skipping through the street. To and Ka-Fai turn the tide of romantic sweetness into a bitter pill to swallow.

“Running on Karma” is a film that is hard to classify. It starts off as an action picture, then adds some romantic-comedy, and finally settles down to a layman’s philosophical treatise on Buddhism. The movie contains a bit of each. Some may find the topic too hard or ridiculous to swallow, but To and Ka-Fai do not, thankfully, give in to a happy-go-lucky ending. Even if the material is armchair philosophy, it does joggle the mind enough to make “Running on Karma” the weightier picture over earlier efforts, “PTU” and “Turn Left, Turn Right.” The film offers many surprises, including a top-notch performance by Andy Lau, and a great way to be entertained. “Running on Karma” attempts to alter our perceptions of reality by asking the simple question: “What if?”