If the name Patrick Hamilton rings a bell, it's probably one that chimes with a certain tone of inter-war urban despair: a recent resurgence of interest in his work means modern audiences are probably more familiar with his novels (including Hangover Square and 20,000 Streets under the Sky) than his plays.

Hamilton's first big success, however, was the Nietzschean stage thriller Rope (a West End hit in 1929, filmed by Hitchcock in 1948, recently revived at the Brockley Jack Studio) and his other plays include Gaslight. With such a pedigree, the revival of a rarely-performed piece by Hamilton is an exciting and tempting prospect. But do Orlando Wells's adaptation and Phoebe Barran's production live up to expectations?

I won't keep you in suspense: the answer's a resounding yes, despite the rather confusing trailer on the Tabard's website, which features a mashup of all the most dramatic speeches yanked out of context and delivered fiercely to camera. There is such a thing as trying too hard, and this show really doesn't need to. Luckily, as soon as the curtain rises the audience is able to relax into the hands of a director and a cast who know exactly what they're doing.

The status quo that greets us in the first scene is as follows: in war-torn Renaissance Franc ethe Duke of Laterraine ("the Land"), played with weary nobility by Michael Palmer, has spent the last 16 years imprisoned with his manservant Gribaud (the excellent Jamie Treacher, mercurial and pathetic in the best sense). Nothing changes and nobody comes, especially not to their rescue: the pair's only amusements are chess and bickering, and Gribaud even cheats at chess. So far, so Endgame-meets-Rosencrantz-and-Guildenstern. But this is no existential stalemate, for soon the prisoners are told to prepare for a visitor: their captor the Duke of Lamorre (Martin Miller).

As this is a taut, unshowy thriller which depends on its plot twists to hold the audience's interest, I won't reveal too much more, but I can say that Jake Mann as new gaoler Voulain manages deftly to combine oleaginous creepiness with wide-eyed sincerity to excellent effect, sometimes in the same sentence. Meanwhile, Martin Miller's Henrician Lamorre, a bluff buffoon in doublet and hose, provides welcome comic relief which only partly veils the unstable threat he represents.

The interplay between captor and captive during the visit depends heavily on Laterraine maintaining the fiction that he's feeble and blind, and this is a superlative piece of physical acting on Palmer's part, extending even into an entertaining game of mental chess which the prisoner (naturally) wins. When the chaotic, babbling Gribaud interrupts this delicately-balanced scene, the sense of danger is palpable: a single unguarded word could threaten the Duke's escape plans, and without him, any uprising to oust Lamorre will fail.

Gribaud, the Duke's only companion, his friend, helpmeet, sparring partner and loyal servant, has gone mad, and in doing so, made himself expendable. But will the Duke have the guts E.M. Forster once hoped for – to betray his country, rather than his friend?

I couldn't possibly comment on what happens next, of course, but the script (a svelte one hour, 40 minutes) certainly kept me guessing, and moreover completely held my attention right to the end. It did have one fewer twist than I was expecting from the marketing (and, yes, the bizarre trailer); but perhaps I've been spoiled by too many Hollywood double-triple-cross plots: sometimes things are exactly what they seem. It's a minor disappointment, in any case, and really nothing anyone could do much about without greatly altering the script. The tight, witty dialogue (which despite the period setting is not, thank God, cod-Shakespearean) is one of the pleasures of this piece, and adaptor Wells has had the sense and sensitivity to leave it largely alone.

Other highlights of the show are mostly visual: Nicki Brown's lighting is subtle and precise, Max Dorey's set is a brilliantly vertiginous, tumbledown tower-room which nonetheless never cramps the actors; and Ameena Kara Callender's costumes – from rags to codpieces – are simply ravishing. But at the core of it all shines the complex and compelling relationship between Gribaud and the Duke, and the question of whether their loyalty to one another can survive the prospect of freedom. Speaking of which...

If you believe the programme notes from producers Mark Perry and Lliana Bird, this is not just a political and personal thriller; it's "a tragic love story" between the Duke and Gribaud. However, while this version of the script will admit of a queer reading, it's certainly not necessary to view it through that lens to enjoy the show. One could say the same about the relationship between Brutus and Cassius in Julius Caesar, but it's debatable how much insight is gained if their closeness is read as that of lovers rather than friends: homosexual rather than homosocial. It was Oscar (Wilde) himself, after all, who said that "friendship is far more tragic than love. It lasts longer."

In either case, after sixteen years locked in the same room, the question at the heart of The Duke in Darkness – would you betray your only friend to save yourself? – is just as appalling, no matter which way you turn (or indeed, swing). The answer's well worth finding out, too, through a great production of an unfairly neglected play. Go and see this thoughtful, nailbiting, beautifully-acted, morally urgent thriller: you won't regret it.

The Duke in Darkness, at Tabard TheatreKaty Darby reviews The Duke in Darkness at the Tabard Theatre.5