Gary Mitchell serves up a new crime comedy at the Lyric Theatre

As usual with the Lyric the set dressing is beautiful. Stuart Marshall's deceptively simple design for Demented, Gary Mitchell's newest play, sees an entire flat dressed for impermanence, for flight.

This is nobody's home, there are no memories here. It's a house furnished in haste by an absentee landlord with a loyalty card at Wyse Byse - and that is perfectly appropriate for the Naughton Studio tonight and the two, desperate men at the centre of this play.

Andrew (Ian Beattie) has been kicked out by his wife and is staying with his father, James ( Roy Heayberd) a situation neither of them is particularly happy with. James suffers from dementia, although its fairer to say that every body else suffers from James' dementia - his favoured form of defence is attack and it's Andrew who bears the brunt of his verbal brickbats - especially galling as his father can no longer remember his name - each time it is mentioned a show-boating James pantomimes frantic searching for him shouting 'Where? Where?' James is sharp and funny but only too aware of his failing faculties and develops elaborate strategies to prove that he is only faking his illness.

These are two of three couples in this play. The next ones we meet are Stacy (Jo Donnelly) and Justin (Richard Orr). At first glance these appear to be thankless, sit-com roles: the stiff with the suitcase and his put upon wife but again as the narrative develops, depths and nuances are filled in, back stories emerge and by the time we meet our last couple James' wheelchair bound neighbour Keith (Michael Liebmann) and the prowling Felicity (Roisin Gallagher) the game is afoot: they are going to rob a bank.

As a central conceit this looks like a misjudged crime-caper farce, and the jokes are played up to the hilt. But thanks to Gary Mitchell's sensitive writing and some clever bits of acting from the cast, the tragedy of the character's situation is never far from resurfacing beneath the thin membrane of good-natured smut. These are the actions of desperate men: Keith has lost his legs, James is losing his faculties and he knows it and Andrew eventually goes along with the plan as a way of looking after his father. There are occasional looks of anguish thrown to the audience from Beattie but Heayberd runs the gamut as James, from passive aggressive to plain aggressive, his James is a tetchy, stifled man, only too aware that his light is dimming and determined to do something to make a change. For all the laughs he generates he seems like a genuine loose cannon.

The acting across the board is excellent as various intertwined motivations are revealed: Gallagher's Felicity reveals herself to be the brains behind the operation, the nexus between these two disparate groups of people and she vamps around the stage making mince-meat of the men. Only Andrew isn't convinced: 'She's a bigger idiot than he is - at least he's got a good looking girlfriend - what does she have?'

Liebmann's Keith is very subtly played in a role that could easily be a caricature: he's a biker with an ever present can of Harp stuck in his leather clad mitt. But there are some beautiful slow, sly reactions from him and he fully rounds out his role. Richard Orr too is great as Justin, potentially the least sympathetic character in the piece, an adulterous banker with a guilty secret. But he invests him with an all too human fallibility (as well as a comically ungovernable lust) which turns him from an obvious villain into an altogether more sophisticated character.

Richard Croxford's direction is brisk and efficient, and the actors run at a fair pace. If the play starts to sag just before the interval it hits the ground running in the second half and never gives up: set piece after set piece and gag after gag. It is pulverising.

An extraordinary example of the farceur's art and testament to Gary Mitchell's skills as a multi-textural writer. This play manages to get the tone exactly right: it treats a serious subject with gravity and taste and a bank heist plot (played out in a kitchen and a living room!) with a deft lightness of touch. Demented wants it all ways and, thanks to the quality of its constituent parts, it damn nears gets it all too.

Demented runs at the Lyric Theatre, Belfast until May 29.