Merritt Wever and Domhnall Gleeson share a volcanic chemistry in HBO’s fun, murky Run

There’s no shortage of chemistry between the two leads of HBO’s Run, a romantic comedy-thriller created by Vicky Jones and executive produced by Phoebe Waller-Bridge. As a reunited couple who get more excitement than they bargained for, Merritt Wever and Domhnall Gleeson bring a powerfully flirtatious verve to every sidelong glance, imbuing each raise of an eyebrow with unspoken promise. Watching Ruby (Wever) and Billy (Gleeson) fumble their way back into each other’s lives after nearly two decades apart is both a scintillating and infuriating experience because, like the protagonists of Fleabag and Killing Eve, they are sexy and maddening people. But as it races toward its conclusion, Run needlessly complicates what is often a refreshing and affecting story of falling in love with illusions of other people—and ourselves.

The latest collaboration for Jones and Waller-Bridge has the aching melancholy of Fleabag, along with Killing Eve’s commingling of danger and desire. But though Waller-Bridge pops up in a cameo late in the season, Jones has the run of the show; she’s created a singular pairing and discrete set of flaws and backstories. There are considerable obstacles facing former college sweethearts Ruby and Billy—namely, the events of the last 17 years of their lives—but they still fulfill a pledge they made to each other at 19 to drop everything and trek across the country by train (and plane and eventually, pickup) if they text “Run” to each other within a very narrow timeframe. That’s exactly what happens in the opening moments of the premiere, a taut and giddy episode that offers viewers the same tantalizing vision of the future that Ruby and Billy see—one in which they try to make sense of their feelings and the consequences sparked by their reawakening.

The dynamic between the former lovers, at once electric and lived-in, is established with little dialogue; Wever and Gleeson are such acutely expressive performers that they communicate decades worth of history with a resigned slump of the shoulder or bite of the lip. When Ruby and Billy do speak, it’s to needle or tempt one another; only rarely do they reveal what they’ve been up to for the last two decades. Neither wants to disrupt the image the other has of them, but as with any relationship, new or revived, their perceptions are gradually revised (or rather, fleshed out) by the truth. At one point, Ruby admits that she’s avoided searching for Billy, who became a New Age-y motivational speaker, online in the intervening years: “I didn’t want your new career as a prick to make me hate you.” As he agonizes over the glimpse he inadvertently gets into Ruby’s current life, Billy wonders just how much he wants to know about the one that got away.

Run is at its best when embracing rom-com traditions, like the will-they/won’t-they and the meet-cute, then just as quickly subverting them. Ruby and Billy’s fateful journey recalls that of Jesse and Céline in Before Sunrise, while their pledge brings to mind any number of sitcom and movie couples—when Run doubles down on the My Best Friend’s Wedding similarities, it results in one of the most affecting and loaded scenes of the whole series.

Their infatuation is the audience’s infatuation. We’re initially thrilled to watch two immensely likable and flawed people taking a chance few of us would, especially in our mid-30s, with all the attendant responsibilities. As Ruby, Wever, who gently bowled over critics last year with a quietly powerful turn in Netflix’s Unbelievable, emits a great sense of longing and restlessness. But Ruby isn’t just a girl interrupted; even if she had to make some tough decisions in the past, her present-day flakiness isn’t readily excused. Gleeson’s Billy is knotted with doubt, which makes his easy smiles around Ruby that much more winsome.

As their backstories emerge, reality sets in, as does ambivalence. Ruby and Billy aren’t able to just pick up where they left off; they have disagreements and even second thoughts while on the train. “I thought seeing you would make me feel good again, but it just makes me sad,” one muses to the other after another bit of personal history is revealed. The audience is similarly conflicted, especially as it becomes clear that a lot of the pair’s problems are self-made. By then, Jones and director Kate Dennis, who helmed the first half of the season, have gotten us to invest in the outcome. But as the obstacles become less personal and more outlandish, the shift in tone threatens to throw the whole thing off the rails. Like Netflix’s Dead To Me, Run hedges its bets, adding external threats that strain credulity. Archie Panjabi is game as another disappointed person from Billy’s past, but as she morphs into an almost Terminator-esque figure, Run begins to lose its charm and complexity.

High-concept shows are nothing new, and a high-concept rom-com could certainly work. By setting the story in the aftermath of an ostensibly happy ending, then interrogating the trappings of happily ever after, Jones was already well on her way. But the late-season developments have the unintended effect of absolving Ruby and Billy of their responsibility, which robs Run of its earlier potency. Like its protagonists, Run makes regrettable choices; hopefully, the show will also have a chance to course-correct in its final two episodes.