Relay review – Riz Ahmed is a fixer on a mission in a throwback thriller

In the wrong, or maybe just less right, hands, the set-up of pacy thriller Relay could have been the set-up for a standard-issue network pilot. A nifty fixer, who finds unique and unexpected ways to assist reluctant whistleblowers as they hand back damning documents, feels like a character who could lead multiple seasons of a solid, if stodgy, NBC drama. But the Scottish writer-director David Mackenzie, whose primary credits include Starred Up and Hell or High Water, is aiming a little higher, something closer to the paranoia and laser focus of 70s and 80s thrillers like The Conversation and Blow Out (something he has made reference to in early press).

When that remains the aim, along with co-writer Justin Piasecki, he does a pretty sterling job at paying homage while avoiding pastiche. His fixer is Ash, played by Riz Ahmed, a man fading into the background, going about his work in New York, avoiding identification, living the life of a ghost. His latest client is food industry employee Sarah, played by Lily James, who uncovered potentially ruinous information that she impulsively made a copy of yet now, after increasingly alarming harassment, she has decided to return. This requires him to act as intermediary, sensitively communicating between the two parties to ensure safety.

Related: Nightbitch review – Amy Adams turns into a dog in rough dark comedy

He does this via a telephone relay system, a service that is primarily used for those who are deaf or hard of hearing that involves one party speaking to an operator, who reads out the typed replies from the other side. They are bound by secrecy laws, so it allows Ash to remain undetected.

It’s a neat device for Mackenzie, and updating the films he’s referencing gives him a way to integrate and pay homage to older technology too (the typing machine used by Ash is charmingly boxy, mobile phones are prioritised for ease but landlines have their place, there’s a punchline involving a vinyl record). As Ash guides Sarah through the maze she’s found herself in with a crack team on her tail (led by Sam Worthington), there are some sharp sleights of hand as we see him outsmart them with trickery involving the intricacies of the postal service, something that’s a lot more fun that it sounds.

Given the nature of his job, Ash is a character kept in the darkness for the most part and it’s left up to some smartly underplayed AA meetings to fill in the gaps. He’s also brought to life by a slowly burgeoning connection with Sarah, something that grows a little harder to believe as it crosses over to flirtation. While Ahmed is entirely convincing, handsome but unassuming, eyes darting around to ensure safety, a plan forever being formulated, James is a little less effective, unable to sell us on the charm and vulnerability that would suddenly cause him to let his guard down.

Related: Eden review – Ron Howard’s nasty, starry survival thriller falls over the edge

With so many New York-set films choosing the ease and affordability of a stand-in city, there’s a thrill to Mackenzie’s on-the-ground authenticity, the kind of film New Yorkers will watch while quietly doing the headwork to place each scene. But in an attempt to accentuate, he gives the film a stark HD crispness that renders it a little soulless visually. It bothered me most during a third-act sequence at a Broadway concerto, the kind of suspense-led set piece that makes us miss the style of a Hitchcock or a De Palma. His attempt at urgent realism also starts to jar with how the story then unfolds, the film dissolving into heightened, credibility-destroying silliness. The subdued carefulness of the buildup gives way to rote, poorly staged action and a twist that might fill in a few plot-holes but leaves us otherwise dissatisfied. What’s funny is that the earlier concern over the set-up being close to a boilerplate procedural drama then feels oddly validated during a mundane end-0f-episode finale which distances us with shooting and shouting, a wholly unconvincing shift that made me mourn the brainier foundation.

It’s a frustrating note to end on, Relay unwisely passing the baton from canny, contained thriller to more routine action.

• Relay is screening at the Toronto film festival and is seeking distribution