It’s all about the children. If an action movie’s job is to kill as many adversaries as possible while retrieving and protecting an abducted child (preferably the protagonist’s), narratively it can put its feet up and dictate the rest. Long before

Denzel Washington was a Man on Fire, long before Liam Neeson’s daughter got Taken, and long, long before the recent, expensive hunk of action cheese "The Gray Man" flew in one eye and out the other, we have yearned as a movie audience to see the kids get home safely, no matter how many corpses litter their path.

Now, on Netflix, comes "The Mother," produced by and starring Jennifer Lopez as a crack sniper and go-between for two of the sleazier arms dealers on the planet. The character has no name. She’s the title, and the 12-year-old child (played by Lucy Paez) she never knew has been raised, happily, in Cincinnati. The beginning of her life had its difficulties: In flashback, one of the arms dealers, played by the sneering Joseph Fiennes, stabs The Mother in her belly mere hours before she delivers the unharmed newborn and disappears into her remote life in Alaska. Fate brings The Mother out of retirement and back into child-protection mode, when the sympathetic FBI agent Cruise (Omari Hardwick) makes good on his promise to let her know when her faraway daughter falls into the hands of mom’s enemies. Those arms dealers: relentless. But The Mother: more relentless.

The movie’s pretty good, especially the first half. Director Niki Caro knows what she’s doing. Yes, some of the dialogue credited to Andrea Berloff, Peter Craig and Misha Green includes lines such as "Treat her as you would a hundred snipers," and setups of comical obviousness. (If you’re an FBI agent with very few lines, and you’re standing by a large living room window and you call The Mother a bad word, odds are 10 million to one you’ll be shot and killed by the time you reach the end of this sentence.)

We can all heckle that sort of writing all day, as we can the entire Man/Woman on Fire revenge genre. But director Caro ("Whale Rider," the undervalued "McFarland, USA," the live-action "Mulan") has a real facility with building routine gunplay – since movie gunplay rarely feels like play anymore, we should retire that word – into crisp, percussively staged and edited suspense sequences set against better-than-usual backgrounds. Plus Lopez glides through all the bloodletting and occasional moments of rumination like a star, because she is one.

The cast includes Paul Raci (Oscar nominee for "Sound of Metal"), who adds a welcome dash of low-keyed realism as The Mother’s military buddy, now living in Alaska, played by British Columbia.

In other scenes, Spain’s Canary Islands portray Havana and its environs, while Gael Garcia Bernal takes the part of the other key sleazy arms dealer. He doesn’t have enough to do, by my reckoning. But the movie’s an overfull two hours as it is. "The Mother" offers some admirable wrinkles along the way; young Zoe endures and expresses more anguish than usual for this sort of plot device, though the movie zigzags from glancing emotional trauma to merry training sequences, where Lopez teaches Paez the fine art of long-distance assassination, as well as planting land mines just so in the snow.

What distinguishes Lopez in "The Mother" from, say, Rachel McLish in an ‘80s movie like "Aces: Iron Eagle III?" Not the T-shirts, certainly. It’s largely the degree to which Lopez (like Washington, Neeson and others) has unlocked the key to underplaying while seething, and letting the rage out precisely when called for. The second half of "The Mother" settles for the usual. But getting there makes for a fairly diverting series of melees in the name of child protection, with services rendered by a tough-love mom who does it all.