It’s commonplace to dismiss a cinematic potboiler involving women as “a Lifetime movie,” but in this case the description is literally true: one of the producing partners of “Lila & Eve” is Lifetime Films. And it is, in fact, also “a Lifetime movie” in the generic sense, though one distinguished by a ferociously committed performance by Viola Davis.

Specifically, this is one of those Lifetime movies about a mother who must deal with the loss of a child, most usually by seeking to bring the person responsible to justice. In this case, the mother’s grief takes her into revenge of the most direct sort, and before long we’re in “Death Wish” territory, with the plot turns growing more and more implausible as the picture lumbers toward what might pass for a happy ending.

As directed by Charles Stone III from Patrick Gilfillan’s script and edited by Robert Lambert, the film introduces Lila Walcott (Davis) in despair over the death of her older son Stephon (Aml Ameen), who was killed in a drive-by shooting near their home. Flashbacks show Stephon’s last birthday celebration with Lila and his younger brother Justin (Ron Caldwell), as well as the incident in which he died.

Lila visits police headquarters for information on the investigation from detectives Holliston (Shea Whigham) and Skaketti (Andre Royo), only to learn that Stephon was apparently collateral damage in the murder of a drug dealer, but no witnesses have come forth to provide the information needed to pursue the case. Her only solace is a support group for mothers who have suffered the loss of a child, and for the angry woman it’s hardly enough.

It’s at the Mothers of Angels, as the group is called, that Lila meets Eve (Jennifer Lopez), an equally angry mother—she lost a daughter, it’s explained—who reluctantly agrees to become Lila’s sponsor. Brassier and more contemptuous of the authorities, she insists that the only way to achieve closure will be to investigate Stephon’s death themselves and find the evidence that will lead to the punishment of those responsible.

So the women establish an unofficial stake-out at the corner where Stephon was killed and confront the newly-installed dealer there. The meeting does not go well: he threatens them with a gun, and Eve responds by shooting him. Lila is horrified by the fact they’ve killed a man, even in self-defense, but Eve assures her that she’ll take care of everything; and when it appears that they’re not suspected of the death, she convinces Lila that they should follow the trail upward from the small fry to the men actually in charge. They work their way up to the rich kingpin, leaving more and more bodies in their wake, and after he threatens Justin, set an elaborate trap—involving an explosion—that will take out the entire upper echelon of the gang. The women’s crusade has aroused the suspicions of Detective Holliston, but in the end his ability to bring them to justice depends on proving that they have no alibis for the nights in question.

Folded into this frankly preposterous plot are Lila’s domestic arrangements, among them taking care of Justin (a bright lad who comes to feel that his mother’s fixation on his brother is unhealthy) and dealing with the gentle advances of Ben (Julius Tennon), a kindly neighbor who obviously has feelings for her. With Eve’s help Lila even begins refurbishing the house on the days when they’re not off doing their vigilante thing; one sequence shows them determinedly repapering the walls. Gilfillan tosses a twist into their relationship in the final stages, but it serves only to make the scenario even less credible.

The only element that really separates “Lila & Eve” from cheap exploitation fare is Davis. Charles Bronson played the avenging angel of Michael Winner’s 1974 film in minimalist style, but Davis takes an opposite approach, portraying Lila’s pain and simmering hysteria as open wounds that have to be healed by extreme action. It’s a volcanically powerful performance. Lopez, by contrast, is just shrilly confident, prodding her companion at every step along the way. The coldness contrasts with Davis’ heat, but the character never moves beyond the stage of a plot device, especially toward the close, and Lopez hasn’t the resources to fill Eve in beyond the surface. The rest of the cast is adequate, but no more than that, and technically the film is merely competent, with Wyatt Garfield’s camerawork not always capturing the action as clearly as it might.

Like all fictional films about vigilantism, “Lila & Eve” raises uncomfortable moral issues, and like most, it skirts them. Should Lila pay for what she’s done in a court of law, however powerful the grief and fear that drove her? It’s an interesting question, but Gilfillan and Stone simply set it aside with a coda that’s meant to be clever but comes across as pandering instead. But then, what do you expect of a Lifetime movie?