Adèle Haenel and Guillaume Canet in The Name of My Daughter (Cohen Media Group)

A mild-mannered lawyer attaches himself to a wealthy casino matriarch. He wins the heart of her free-spirited daughter and then reveals his true colors as a ruthless sharpie, turning daughter against mother in a battle for the casino’s future. A mafia boss zeroes in on the action, keeping a close eye on the women—and on the turncoat lawyer. Payback’s on its way, right?

You would think. But revenge or even a resolution fails to materialize in a film that starts hard and flinty-eyed and then strangely collapses into two unrelated stories of diminishing energy and dramatic impact. Veteran director André Téchiné whips up the tension, only to mystify—and frustrate—when expected vendettas never take place.

Based loosely on a true story, In the Name of My Daughter unfolds on the gorgeously lit and shot Cote d’Azur. Catherine Deneuve, now in her eighth decade, offers up yet another warhorse turn as casino magnate Renée Le Roux, cynical, worldly, but also loving and indomitable. Deneuve’s scenes in the closed, elaborate world of the gambling parlor are among the movie’s canniest. Her old-pro performance contrasts intriguingly with a naturalistic turn from Adèle Haenel as Renée’s daughter, Agnès, a bourgeoise rebel more fragile than her earthy, athletic exterior suggests.

Into their lives slithers the lawyer Agnelet (Guillaume Canet, crafty and enigmatic), whose name suggests “lamb,” which he is not. He wins Renée over by making risky moves on her behalf to save the casino from a brazen mafia takeover, and he wins Agnès’s heart by playing the shy nerd who has to be seduced. Both women will see what the cold, manipulative Agnelet is capable of when things do not go his way. In the meantime, the film’s early stretches positively hum with drama. Every scene bristles with a revelation, a confrontation, a surprise, or a diss. The stakes are high, the mood dark with betrayal in the golden afternoons.

In an atmosphere of fatalism, some lovely scenes unfold. Agnès performs an African dance for the restrained Agnelet as amusement, wariness, and grudging affection play across his face. Their illicit encounters in the French countryside burn with passion. In addition, music plays an unexpected part. The close mafia family sings a foreboding Corsican ballad together on their elegant terrace. Ejected from her stronghold, Renée warbles an Italian version of “Stand by Me” along with her chauffeur. Poignant moments don’t foreshadow much, though, because at this point the movie takes several wayward turns.

In the Name of My Daughter suddenly shifts focus from casino power games to Agnès’s fruitless love for Agnelet. Mind you, this is a man who flaunts his amorality, who makes no bones about being involved with other women—one of whom archly taunts Agnès—and who warned Agnès that he was unavailable. Agnès writes him obsessive letters, weeps, calls and hangs up, gets blown off, and stalks Agnelet at his child’s school. It’s a bit much and a bit of a bore.

And then the film takes off on a completely bewildering trajectory, shifting ahead three decades. Like the mafia in the movie’s plot, Agnès has completely disappeared; Renée (coming down in the world and looking like a pied-noir cleaning lady) insists on bringing charges against Agnelet for her murder 30 years earlier. We find ourselves deep in a dusty courtroom drama, with flimsy accusations hurled against the impassive Agnelet, now done up in weird old-folks macquillage. A series of titles hastily wraps up the plot, which, like many trials, ends in unsatisfying, inconclusive legal details.

What happened to this movie? A breakneck pace, prickly characters, and high stakes kicked off In the Name of My Daughter to such a bracing start. It’s tempting to lament the film’s lost potential, but the loss is so sudden and so complete that astonishment usurps disappointment. I’d pay good money to see a remake, this one with the dramatic and bloody vengeance the story deserves.