Steven Soderbergh’s Black Bag dials back his usual visual eccentricities, opting for a slicker, more restrained approach. And it’s all the better for it. The theoretical centrepiece of the drama is Severus, a cyber-worm capable of triggering nuclear-level destruction. But Severus remains an abstract mystery, its real power lying in how it spins a web of suspicion and betrayal among a clique of elite British intelligence officers and the married couple at its centre.

Michael Fassbender and Cate Blanchett anchor the film with icy, magnetic performances that make every glance feel like a negotiation. Fassbender’s George Woodhouse is a walking lie detector, emotionally locked down and perpetually calculating, who moves with the controlled precision patented for the actor's roles in The Killer and Prometheus. Opposite him, Blanchett’s Kathryn St. Jean is all slinky, old-world charm and guarded intent, a woman who knows exactly how to play the hand she’s dealt. Their performances are slick and simmering, though I'd have liked a bit more flirtatious fun between the two. Blanchett’s wig is initially distracting, and paired with the couple’s clipped dialogue and the low-lit interiors, takes a moment to adjust to – but once it settles, the chemistry between them hums beneath the surface.

The title, Black Bag, refers to top-secret intelligence, the kind of intel you wouldn’t even share with your spouse. It's the phrase the couple utter to one another in response to questions they can’t answer; a convenient catch-all and shut-down for any and all kinds of activities, dealings and movements. But it starts to act as a metaphor for the betrayals and double-dealings circling George and Kathryn’s marriage. When George’s contact Meacham (Gustaf Skarsgård) reveals that a mole within their ranks has stolen Severus, George faces an unsettling directive: if Kathryn is the traitor, he must be willing to take her out, and consider the possibility that she is planning to do the same to him.

The tension peaks at a dinner party held in the couple’s posh London townhouse. The guest list doubles as a lineup of suspects: George’s right-hand man, Colonel James Stokes (Regé-Jean Page), agency psychiatrist Dr. Zoe Vaughan (Naomie Harris), bitter womanizer Freddie Smalls (Tom Burke), and his sharp, much-younger girlfriend and promising new recruit Clarissa (Marisa Abela). Each guest can sense the evening’s ulterior motives.

George spikes the chana masala with a sedative, hoping the loosened tongues will reveal the mole. (“Darling, you must not dose our guests,” chides Kathryn.) The meal unravels into uncomfortable oversharing, but the pacing of the scene – a slow build toward unravelling civility – could’ve leaned harder into the film’s undercurrent of dark humour and marital gamesmanship. Under George’s prodding, Freddie’s extracurricular activities in hotels come under scrutiny, enraging Clarissa and ratcheting up the tension. The secretive nature of the agents’ work casts a long shadow over every relationship in Black Bag. It breeds a toxic blend of distrust and co-dependency as these spies can only trust those who understand their world, yet the very nature of that world means they can never fully trust each other. “We’re all professional liars,” complains Clarissa. “How can you tell the truth about anything?”

Among the supporting cast, Abela shines as the deceptively sharp Clarissa, balancing youthful charm with an undercurrent of seasoned savvy. Pierce Brosnan also makes a memorable turn as Arthur Steiglitz, the dapper, ice-veined head of NCSC. His polished exterior barely masks a ruthless survival instinct, a point underscored by a darkly hilarious scene where he eats a plate of live Ikizukuri sashimi without flinching.

Soderbergh (working under his usual cinematography pseudonym, Peter Andrews) ditches his more experimental tricks for a polished, kinetic look. David Holmes’ moody, percussive score underscores the film’s elegant pulse, keeping pace even as the plot coils tighter.

Black Bag doesn’t aim to be a globe-trotting, action-packed spy epic. It’s sleeker, smarter, and more intimate; a high-stakes marital chess match. The real tension isn’t in Severus or international politics, but rather in the seductive, unsettling question of who’s truly watching whom.

Soderbergh, ever the master of controlled chaos, tucks this one away like a perfectly packed suitcase: neat, sharp, and deceptively weighty. It may not stand the test of time as well as some of his other work, but as a quick, sophisticated trip into a very dark world, Black Bag does the trick impressively.

• In cinemas now. Watch the trailer below: