Gun-su (Lee Sun-kyun) keeps many secrets in the South Korean thriller “A Hard Day.” (Kino Lorber)

If everything that goes wrong for the hero of “A Hard Day” actually took place during a single 24-hour period, it would be a day to rival one of Jack Bauer’s worst. As it is, the action of this highly watchable South Korean thriller — which centers on a police detective (Lee Sun-kyun) who, on the way to his mother’s funeral, accidentally runs over a man — transpires over the course of about a week or so.

That’s long enough for the desperate cover-up that opens the film — with a darkly comic sequence set in a funeral home where the coffin occupied by the officer’s mother’s affords a convenient hiding place — to come unraveled. A few days after the accident, the detective, Gun-su, starts receiving anonymous phone calls from a mysterious witness to the hit-and-run. It isn’t long before we learn the identity of both the victim and the caller. But the film, by writer-director Kim Seong-hun, manages to throw plenty of surprises our way, up to and including the fantastic final shot of the movie, which is as unpredictable as it is satisfying.

“A Hard Day” may be no picnic for Gun-su, but it’s great fun for fans of Tarantino-esque twists, violence and sick humor.

If there’s a quibble to be had, it may be that the movie’s star simply isn’t well known enough in the United States to instantly signal that he’s the good guy. Gun-su’s early actions — and the fact that his unit is being investigated by internal affairs for bribe-talking — create a certain emotional confusion for us at the beginning of the tale: Are we supposed to root for or against this guy?

It takes a while before our sympathies align with him, thanks to extenuating circumstances that make Gun-su’s behavior — self-serving at best, heartlessly amoral at worst — somewhat more palatable. Once that connection kicks in, it’s easy to like this recently divorced dad who’s devoted to his daughter, as well as his sister and her struggling husband. Gun-su’s mounting tribulations just make him more relatable.

It’s just as easy to like the film, which keeps things breezy and cartoonish, despite a fairly high level of violence and some mildly stomach-turning moments involving an unexpected hiding place for a key. You’ll be glad that “A Hard Day” isn’t happening to you, but you won’t regret observing it all from a safe distance.

Unrated. At the Angelika Pop-Up at Union Market. Contains violence and obscenity. In Korean with subtitles. 111 minutes.