Run begins like a horror movie. Ruby (Merritt Wever) is sitting in her parked car radiating suburban housewife ennui. She’s trapped inside her life, just as she’s trapped inside her vehicle, which she’s parked so closely to the one next to it that she can’t open the door. She answers a call from her oppressively doting husband, who really needs his schmoopy to hurry home to field the delivery of some new stereo equipment. She parrots back an “I love you” with annoyance on her face. Then her phone beeps. As she reads the one-word text—“RUN” —the soundtrack becomes a piercing thrum, the kind that suggests a boogeymen of some sort will soon appear. Ruby starts to shake. Is someone watching her car? Is she in danger? She tries to flee. Then, she reconsiders. The score is still pitched to extremely ominous as she taps back a response in kind: “RUN.”

Ruby scrambles out of her car and makes a mad dash for the airport: The show is off, speeding up to a sprint that never stops. The horror vibe drops away, and the show becomes a kind of zippity doodad, a high-concept, sexy, genre-jumping, romantic-comedy thriller as breakneck as a malpracticing chiropractor. Years ago, when they were still in college, Ruby and her then-boyfriend, Billy (Domhnall Gleeson), made a pact that if they ever exchanged “Run” texts, they would both ditch their lives, head to Grand Central Station, and board a sleeper train, heading across the country. They are now making good on that promise.

Ruby and Billy want to see each other, but even more, they want to see the promising, less encumbered selves that they used to be: the aspiring architect so confident in her own capabilities and future that she would break up with a man she loved to pursue her career; a guy with the charm and insight to be a self-help guru, but not yet an oleaginous huckster on the TED talk circuit. They arrive DTF, breathless, and empty-handed but for their very hefty emotional baggage. Running is supposed to be an escape from the hash they have made of their lives, but their escape becomes its own kind of hash. As this happens, the horror opening starts to seem less like a fake-out and more like a hint: There may not have been a literal killer outside Ruby’s car, but that doesn’t mean lives weren’t destroyed.

The show becomes a kind of zippity doodad, a high-concept, sexy, genre-jumping, romantic-comedy thriller as breakneck as a malpracticing chiropractor.

Run (which premieres Sunday night on HBO) was created by Vicky Jones, the director of the original staging of Fleabag. (Phoebe Waller-Bridge is one of Run’s executive producers, and she appears in the fifth episode to demonstrate that there’s at least one thing she can’t do: an American accent. Honestly, thank goodness.) Like Fleabag, but even moreso, Run is a unique amalgamation of genres and moods, never quite settling in, constantly switching tracks. As Billy and Ruby sniff each other out in the first episode, their sexual chemistry is so potent it basically emits a funk. Both of them leave an early conversation to masturbate in the train bathroom. They play word games and mind games and nuzzle at one another like cats in heat, while they also bicker and lie and chicken out. For a while, the details of the lives they fled, slowly revealed to one another and the audience, keep dampening the mood. Their reunion keeps getting interrupted by the present, which is full of partners and children and stalled careers—a raucous ghost party crashed by reality.

But the sexytime fizz of the opening episodes rapidly—everything in this show is rapid—takes a backseat to wilder, more Hitchcockian, action-movie swerves. As Ruby and Billy hop on and off the train, the tension ratchets up, the momentum builds, the consequences get stiffer. They escaped their lives, but are they going to be able to escape their escape? It’s a critical sin to ding a show for not being the version of itself that you wish it were, but Wever and Gleeson exchanging sharp, goofy, flirty banter; insults; and psychological insights in a swoony trans-American throwback setting is not the kind of treat one gets every day. I could have done a few more episodes in that mode before the series, so purposefully, goes off the rails.

As Ruby and Billy pick up speed, a runaway couple barreling West, one is left to wonder, fist in mouth, if they will gracefully pull into a station or smash into multiple vehicles on their way through a building. Having watched five of seven episodes, all that was sent to critics, I can’t say for sure which way it will go. Velocity is thrilling, but it can also be calamitous. Remaking one’s life is probably easier to do at slower speeds. Running is fun, but, in the end, it’s no way to hide.

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