From left to right: Ralph Fiennes, Dakota Johnson, Matthias Schoenaerts, and Tilda Swinton in A Bigger Splash (Jack English/Twentieth Century Fox Film Corp.)

A motormouth collides with a mute on an Italian island—which one of them will end up silenced for good? Two crash-bound A-level players share a charged history of fame, sex, and manipulation, and the clash of the titans will take their type-B partners down with them. At its worst, Luca Guadagnino’s A Bigger Splash is a hothouse of heavy-breathing self-importance, flailing for Antonioni or Polanski portent. At its best, it’s a refreshingly cynical thriller with two ace performers pushing edgy parts way over-the-top.

Rock star Marianne Lane (Tilda Swinton) has recently undergone surgery to repair her injured vocal cords, and talking is off limits. She’s basking in the sun on the secluded Italian island of Pantelleria with hunky boyfriend Paul (Matthias Schoenaerts), with whom she savors a warm, sexy bond. Who should show up uninvited but erratic old love, Svengali, and drug crony Harry (Ralph Fiennes), with his sultry young daughter Penelope (Dakota Johnson) following behind. Trouble, anyone?

Marianne may be silenced, but Harry’s seems to have taken a vow to never shut up. Part Pied Piper and part shit-stirrer, exuberant Harry loves to strip off his clothes and dive-bomb into the villa’s swimming pool. Or dance lewdly to a full-length rendition of the Rolling Stones’ most obnoxious hit, “Emotional Rescue.” In a shrewd turn, Fiennes lets us see the reptilian calculation and rapacity crouching behind Mr. Life of the Party’s grin as he tests the boundaries of those around him.

A recovering rock star’s mutism might seem gimmicky beside Harry’s nonstop babbling, but Swinton turns in a performance that makes the conceit feel effortless. She blends rock star hauteur with an earthy abandon betraying inner contradiction; this woman enjoys satisfying sex with manly Paul, but her restlessness matches her more naturally with Harry. Tense and watchful, Marianne waits for the other shoe to drop. Paul, on the other hand, underestimates temptations and thereby falls prey to them. Schoenaerts has made a career out of playing watchful, stolid himbos. He’s credible here, but it may be time to try something new.

According to press reports, Tilda Swinton felt she had “run out of things to say” in cinema and only agreed to take the part of Marianne if it involved little or no dialogue. Swinton was wise, because Splash’s dialogue falls short of the diamond sharpness to reflect the maneuvers of observant, worldly people. Fiennes works overtime to make his bloviations glint with the quicksilver charisma Harry needs to possess. Schoenaerts murmurs monosyllables. The film’s biggest victim is poor Dakota Johnson, saddled with the most vacuous lines—and part—written for a young actress in a long, long time. Penelope means trouble, but boy, is her dialogue lame. Tossing off pouty whatever-isms, Johnson telegraphs wantonness with a nonstop seductive side-eye, fingers playing suggestively around her lips in a way that recalls Alotta Fagina’s vamps from the first Austin Powers movie. Her character forms a one-note dead spot in a movie that points out its characters’ flaws with lethal precision.

Although one might dismiss Splash because of such a misstep (and other, more lurid ones), the movie gains momentum and menace. Predators size up their quarry. Head trips—and Harry—grow nastier. Betrayals mount. The cinematography creates a sense of disorientation with panoramas that make the island look like a windswept heath and interiors like a trap. And the violent endgame of a long-building confrontation brings a nosy outsider into this festering ménage in the form of a puffed-up Italian cop who may change the rules of the game. A sheepish, deflated ending seems about right to reveal the scornful misanthropy lurking beneath polished surfaces (wardrobe courtesy of Raf Simons).

A Bigger Splash can be silly and full of itself. But its spite and spirit of betrayal play for keeps, and they will get their hooks into you.