“Stranger Things: The First Shadow,” a London theater show based on the Netflix series, pummels the audience with sensory overload and its lavish budget.As theatergoers took their seats, a buttery waft of popcorn in the auditorium was an indicator of what was to come. “Stranger Things: The First Shadow” — a spinoff of the hit Netflix series, “Stranger Things” — brings a high-octane, TV-movie sensibility to the stage, pummeling the audience with horror-show frights and sensory overload: eerie smoke effects, mind-boggling levitations, scary vocal distortions reminiscent of “The Exorcist” and noise — so much noise.Directed by Stephen Daldry (“Billy Elliot: The Musical”; “The Crown”) and written by Kate Trefry and Jack Thorne in collaboration with the TV show’s creators, the Duffer brothers, the show runs at the Phoenix Theater, in London, through Aug. 25, 2024. It’s a gaudy, vertiginous fairground ride of a play, exactly what you’d expect from a show co-produced by Netflix: Cheap thrills, expensively made.“Stranger Things: The First Shadow” is billed as a prequel to the Netflix series, which is set in the fictitious town of Hawkins, In., during the mid-1980s. The location is the same, but the year is 1959, and the play tells the origin story of Henry Creel, who appears as a malevolent sociopath in Season 4. We meet him here as a troubled, withdrawn adolescent (played with great aplomb by Louis McCartney) burdened with psychic, clairvoyant and telekinetic powers of unknown provenance.Henry, a newcomer to Hawkins, strikes up a tentative friendship with another oddball, Patty Newbie, played with a winning blend of naïve compassion and halting self-doubt by Ella Karina Williams. The two youngsters bond over their shared, deeply uncool, love of comic books and, somewhat improbably, land the lead roles in their high-school musical. When several of its cast members find their household pets mysteriously killed, Henry appears to be implicated. His peers take it upon themselves to investigate, and stumble, “Blair Witch”-style, into a baroque nightmare.Henry and Patty Newbie, played by Ella Karina Williams.Manuel HarlanAmid the horror, the play carries a sentimental message about young misfits finding solace and community. Patricia, an adoptee, never knew her mother (“My whole life I’ve been the girl from nowhere,” she laments,) and feels a kinship with Henry because he is misunderstood. He reassures her by pointing out that many of their favorite comic book characters are orphans: “Having no parents is basically a prerequisite to being a superhero.” Similarly, Henry is desperate not to let his strange powers define him. (He insists: “I’m not a freak! I’m normal!”)In these respects the tale is redolent of Young Adult fiction, but the can-do vibes are served up with a bleak twist, since the odds — as we know from Season 4 — are stacked against Henry. A research scientist, Dr. Brenner (Patrick Vaill), ostensibly enlisted to help him, has nefarious motives; the influence of Henry’s father, Victor (Michael Jibson), who has severe PTSD from World War II, is also a source of intrigue. All avenues lead, inexorably, to a big conspiracy involving a secret government program. The supporting cast comprise a panorama of recognizable social types — dumb jocks, deadbeat boyfriends, vapid bimbos, oafish policemen — whose antics provide light relief.Miriam Buether’s set evokes 1950s small-town life with a nostalgic, homey touch: a crescent of school locker rooms for the high school scenes, the community church and a local liquor store are elegantly rendered. Later on, a government psychiatric facility is a neon-lit, white brickwork affair, cold and clinical.In the show, Henry meets with Dr. Brenner (Patrick Vaill), right, a research scientist with questionable motives.Manuel HarlanSome of the backdrops are staggeringly elaborate. The opening scene, depicting a nautical disaster, is like something from a Hollywood action movie. In keeping with this aesthetic, the sound, by Paul Arditti, is quite simply relentless. Thunderously loud crashing sounds occur with nerve-shredding frequency — the “jump scare” technique beloved of horror movies. Henry’s paranormal powers are obscurely connected to electromagnetic energy, so there are lots of buzzing electrical noises whenever he has one of his moments.In its totality, the production is lavish to the point of embarrassment, and the sheer scale of the thing is hard to reconcile with the play’s rather modest intellectual aspirations and lack of originality. One is left simultaneously impressed and a little bewildered. Haven’t television and cinema already got these bases covered? Is this what theater is for?“Stranger Things” first aired in 2016. It’s over four years since Mike Hale suggested, in his Times review of Season 3, that the show might be suffering from “franchise fatigue.” The original concept had a certain straightforward appeal — weird goings-on in a backwoods town, sinister machinations of shady state agencies, sympathetic nerds getting a chance to shine — but it was never quite strong enough to sustain serious longevity. The show powered on regardless, because there was money to be made.“Stranger Things: The First Shadow” achieves what it sets out to do, and die-hard fans will surely lap it up — but it may well prove to be a death throe. The real spectacle here is that of a franchise eating itself.Stranger Things: The First ShadowThrough Aug. 25, 2024 at the Phoenix Theater, in London; uk.strangerthingsonstage.com. More