The eeriest scene in the gripping techno-whodunit “Searching” consists of little more than a computer screensaver, glowing silently in the dark like a jellyfish. A series of incoming call notifications pop up on the screen, but the computer’s owner, David Kim (John Cho), is asleep and thus unaware that his teenage daughter, Margot (Michelle La), is desperately trying to reach him.

The moment takes on layers of Hitchcockian dread and a paralyzing sense of helplessness: Thanks to bad luck and human error, not even the devices that connect us 24/7 can tell us everything we want to know.

The dubious paradoxes of internet technology — its power to inform and deceive, to connect and alienate — are at the heart of this ingeniously high-concept thriller from writer-director Aneesh Chaganty. A former Google employee making a sharp, confident feature debut, Chaganty employs a formal gimmick that clearly reflects what he knows, but also what any 21st century screen addict knows. Unfolding entirely on a series of computer and phone displays, “Searching” both captures and defamiliarizes an experience that most of us would consider mundane, even banal.

This isn’t the first movie to turn FaceTime chats and browser windows into the stuff of a intriguing, sometimes uncomfortably voyeuristic drama. Earlier versions of this conceit played out in the 2014 shocker “Open Windows” and the recent “Unfriended” horror movies, which were about computer owners being terrorized by off-screen psychopaths. The novelty was that those thrillers played out in real time, so that you, as a viewer, felt unsettlingly hard-wired into the user experience.

“Searching” is no less accomplished in its accurate depiction of the online world, but it doesn’t play out in real time. The mystery here, in which a father tries to find his missing daughter by digging into her online history, plays out in a less sadistic, more intimate register, and it benefits from having someone as recognizable and appealing as Cho in the driver’s seat. Because his story unfolds over the course of a week, Chaganty relies on familiar narrative techniques such as exposition and montage, and he and his ace technical collaborators maintain visual interest by continually reframing David’s screen with strategic cuts and zooms.

The prologue compresses more than a decade of family life into a laughter-and-tears montage, composed from photos and videos stored on the Kims’ desktop computer. We watch as David and his wife, Pamela (Sara Sohn), happily raise Margot (played by a few actresses of different ages), their lives a flurry of piano lessons and morning jogs. There are highs and lows, none lower than Pamela’s difficult battle with cancer.

The story proper picks up sometime after Pamela’s death. David has moved on with Margot, who is by all appearances a smart, well-adjusted 16-year-old, at least from our brief glimpse of her chatting online with Dad. The actors have a lovely, unforced rapport that toggles gently between affection and exasperation: When David playfully texts Margot reminding her to take out the trash, he includes a photo of the overflowing can. Margot promises she’ll take care of it when she gets home.

Except that she never makes it home, and David soon finds himself pulled into a mysterious missing-person, one that unspools online in a slow, unsettling and realistic pace. The movie is so insistent on plausibility that it takes several hours before David even realizes that Margot might be in serious danger.

At the recommendation of Det. Rosemary Vick (Debra Messing), David begins searching Margot’s laptop for clues to her disappearance, with some help from his laid-back brother, Peter (Joseph Lee). Dad’s sleuthing generates some sly comedy, but he turns out to be as tech-savvy and resourceful as he needs to be as he pores over Margot’s email and social-media accounts, calls up her Facebook contacts and tries to piece together her last known whereabouts.

The heart of the investigation, and the movie, is a trove of old live-cast videos that Margot had recorded and saved. Watching them for the first time, David begins to appreciate how much he didn’t know (or care to ask) about his daughter, namely how profoundly lonely she had become following her mother’s death. In these moments, “Searching” poignantly explores both the comfort and the isolation that technology can breed, even as it considers the lasting effects of grief. It also satirizes the ways in which that grief can be mocked and exploited, through mindless online gossip, sensationalist media coverage and the performative sympathy of onlookers.

“Searching” is nothing if not ambitious, and its rapidly accelerating second half is jammed with bold twists, red herrings and breathless confrontations. It’s also here that the movie begins to slacken its grip — partly because some twists beggar belief, and partly because they strain the limits of the online-all-the-time interface. Much of the plot has to be recapped via TV news footage, forcing the picture to behave like a more conventional thriller and muddying the question of whose perspective we’re following.

The movie is at its strongest when that perspective is David’s. Cho gets the kind of actor’s showcase that has eluded him too long. He runs the full gamut of fatherly emotions like a pro, escalating from mild panic to violent outrage, but the key to Cho’s charisma is that he can just sit there and still hold your attention. He may just be a guy in a plaid shirt mumbling into a webcam, but that doesn’t make him any less of a movie star.

“SEARCHING”

****

(PG-13, 1:42)