Spy tales and romantic stories make for strange if complementary bedfellows. Both, after all, depend on a building of trust between individuals. A spy is only as good as how well they can quickly and efficiently connect with strangers, often creating a makeshift intimacy that’ll be nurtured in due time. The terms may be different during a romantic meet-cute but the comforting sense of being seen by someone you just met — not to mention the thrill of what they may bring out in you and how they may change your life — is not too dissimilar.

In Adam Patterson and Declan Lawn’s diligently crafted British caper “Rogue Agent,” the lines between a rakish spy and a dashing lover are blurred in the figure of Robert Freegard (James Norton), a real life individual who leveraged his alleged spy credentials toward less than savory ends.

“Rogue Agent” opens with some requisite historical context. Title cards remind us that in the 1990s, the Irish Republican Army was waging a bombing campaign in England, causing MI-5 to recruit freelance spies to help root out possible culprits. Gemma Arterton’s voiceover helps further characterize the seductive spy we meet, first in 1993 when he recruits three unsuspecting college kids and nine years later when he flirts with Arterton’s Alice Archer in London. He knows how to gain your trust instantly: He looks into your eyes long enough to register their color.

Initially taken aback by his advances, Alice does slowly fall for this handsome stranger who seems intent on throwing her off every chance he gets (“You’re so fucking random,” she beams at him at one point, perplexed at how smitten she’s become). He’s both forward and shy, eager to get Alice to make the moves that land them both into a comforting relationship. Finding herself anew, Alice begins to daydream of leaving her lawyering days behind. She could even open a business with this luxury car salesman who shares very little about his own life. He is delectably intoxicating, after all. Just try not to fall for him as he dances to George Michael in nothing more than a striped towel!

Theirs would be a blissful romantic drama were it not for two things: those pesky phone calls Robert gets from a girl named Sophie and the fact that a private investigator Alice hires can’t find anything on Robert. “He’s a ghost,” she’s told. It’d be enough to make any woman wary — which is why she’s so blindsided when he confesses he’s a spy.

As a cover story, it’s airtight. It explains his absences and his caginess. It’s almost too perfect an alibi; might it actually be a lie? It’s a question that Sophie herself (Marisa Abela) cannot bring herself to ask, especially after having blindly followed Robert’s orders since she was first recruited in college a decade prior. What else has she been doing if not working as a spy-in-training for someone she believes is an officer of MI-5?

“Rogue Agent” at first toys with the possibility that Robert may well be telling the truth. Until, that is, Alice learns firsthand just how skillfully he’s played her — and maybe many others too. Writer-directors Adam Patterson and Declan Lawn have adapted an unpublished article by Michael Bronner (a co-writer on the film) that, especially when spelled out in writing, has the making of a thrilling page-turner.

Yes, this near-implausible yarn is quite gripping. On the page, at least. And on the screen, at times. With a cad like Robert at its center (charmingly played by Norton, who served as a producer on the film), the story of his downfall at the hands of a heartbroken but driven woman who refused to see herself as his victim (“You have not broken me,” Alice tells him) is quite enthralling. It’s also gorgeous to look at, with handsome production elements all around.

With a thesis around how spies (and scammers) know how to tell those they lie to the stories they wish to hear, Patterson and Declan’s film is a finely crafted caper whose own clipped storytelling can never quite match Robert’s own slippery appeal. As a revenge spy thriller of sorts (the kind that seems tailor-made for a TV miniseries these days), “Rogue Agent” is an engaging affair. Much of it is due to Arterton, whose steely performance firmly anchors the film even during its most improbable twists and turns — especially as it careens toward its inevitable conclusion and its all too pat final image.