Jackie Powers (Scott Caan), a hit man, enters a diner to collect a debt from Walter Boggs (J.K. Simmons), but when both of them start shooting at each other, an innocent bystander gets shot in the crossfire. He takes Lola Brisky (Marianne Rendón), a waitress, as a hostage while fleeing the diner. Meanwhile, he has to come up with money to get his teenage son, 15-year-old son Billy (Dash Melrose), out of a juvenile detention center.

      The screenplay by Scott Caan is a mildly entertaining B-movie that bites off more than it could chew with its overwrought plot. There are shades of Tarantino, but, for the most part, One Day as a Lion lacks the wit, boldness, dark comedy and pizzazz found in Tarantino films like Pulp Fiction---which has a very memorable diner scenes. The plot unfolds linearly which makes it easy-to-follow and conventional. However, there are too many underdeveloped subplots and characters, including a contrived romance between Jackie and Lola. Oh, and there's also crime boss Pauly Russo (Frank Grillo) Lola concocts a plan to steal from her dying mother, Valerie (Virginia Madsen), to help Jackie get the money he needs to get his son, Billy, out of jail. Then there's Jackie's toxic relationship with his ex, Taylor (Taryn Manning), Billy's mother. Billy clearly doesn't have any good role models in his life, so it comes as no surprise that he has issues. Like father, like son. One Day as a Lion doesn't bother to explore any of its themes or to get to know any of its characters. Those shortcomings would've been fine if it were more focused, lean and gripping on a visceral level.

      Scott Caan does his best to rise above the shallow screenplay with his charisma as do the other fine actors including J.K. Simmons and Frank Grillo in their supporting roles. The cinematography is fine without being excessively stylish or overly-edited, while the pace moves briskly enough. There's nothing exceptional about the action scenes---if you're looking for truly spectacular action scenes, see any of the John Wick films which sets the high. Perhaps the best thing about One Day as a Lion is its less than 90-minute running time which means that it doesn't overstay its welcome or become too exhausting. At a running time of 1 hour and 27 minutes, it's mildly entertaining and well-cast, but undercooked, witless and only intermittently suspenseful.