Half Moon Lake is a natural lagoon located in the unlikely setting of the Lenadoon housing estate in West Belfast. A favoured dumping ground for supermarket trolleys, it witnessed numerous knee-cappings and punishment beatings during the Troubles. By day it doubled as a place to fish, scramble, and climb trees for successive generations of Lenadoon youngsters.

Sean Doran, the sole character in Pearse Elliott's new play Man in the Moon, was one of them. On a twilit evening he returns to the Half Moon, tieless but smartly suited, with a large plastic bottle of cheap cider as company. Doran has recently lost his job, rarely sees the daughter he had with an ex-girlfriend, and generally has little in his life to laugh about.

From his demeanour you would hardly guess it, for Doran is an archetypal Belfast 'character', forever wisecracking, telling tall stories, and lacing his monologue with liberal dosages of the f-word, c-word, and other profanities. He's hyperactively personable, and bursting with tales of derring-do about the old days with the "Half Moon crew", before adulthood arrived and life turned serious.

Beneath Doran’s bonhomie, however, there are demons lurking. "Only a handful" of the fifteen members of the Half Moon crew, he tells us, are still living. The others killed themselves, some at the very lake where they used to play together. The scenario is fictional, but not unrealistic: Elliott, who grew up in West Belfast himself, describes in a programme note how leafing through an old yearbook recently revealed to him the shocking number of his former schoolmates who had since committed suicide.

It gradually becomes evident that Doran's obsessive story-telling in the play is fuelled by a need to not think about the unthinkable, or speak about the unspeakable. Ghosts of dead suicides stalk his memories, causing rapid mood-shifts as he finishes a story, his natural ebullience pricked and instantaneously deflated.

These abrupt lurches into introspection are consummately negotiated by actor Ciaran Nolan, working in the appropriately intimate space of the Baby Grand theatre at Belfast’s Grand Opera House. At these crucial points of transition, Nolan’s is the art that conceals art: an anxious twitch, a sudden draining of his animated features, and suddenly the world of hopelessness and desperation beckoning him is graphically apparent.

Nolan is equally convincing as Doran the extrovert, gleefully recounting past escapades, mimicking the gallery of Half Moon characters who populate his monologue, and throwing a particularly excruciating selection of dad-dance movements as he recalls wild evenings spent together. It’s a performance energised by Nolan’s total immersion in the character, and his absolute command of local idiom and inflections.

Tony Devlin’s limpidly intelligent direction helps immensely. He too knows the speech and thought rhythms of West Belfast intimately, and has the knack of giving Nolan considerable freedom of expression, while retaining cohesive grip on the clear structural outlines of Elliott’s writing. Ciaran Bagnall’s simple painted backdrop – a white moon silhouetting a nocturnal city skyscape – neatly complements Devlin’s clear, uncluttered conception, and needle-sharp technical cues maximise the impact of Justin Yang’s rock-based soundtrack.

As Act Two progresses, the feeling grows that Man in the Moon is skirting imminent tragedy. Doran’s suit, we learn, is worn because his younger brother’s funeral happened that morning – he committed suicide, like his elder brother before him. As Doran scans the waters of the lake, swilling mouthfuls of cider, head full of painful reminiscences, you fear for him. Is he fated to follow so many fellow-members of the Half Moon crew into premature oblivion?

The play’s conclusion may divide opinion. Some of what Doran says ring less true than what we’ve heard from him previously, and imparts an element of anti-climax that could probably be averted by a moderate amount of re-writing.

As it stands, though, Man in the Moon is a brave and stirring piece of theatre, addressing in an unwaveringly humane and articulate fashion a desperately sensitive and still widely misunderstood subject. Ciaran Nolan’s marvellously engaging, expressive performance is in itself unmissable, and marks a new high-point in this rising young actor’s already impressive career trajectory.

Terry Blain is an arts journalist and cultural commentator, contributing regularly to BBC Music Magazine, Opera magazine, the Belfast Telegraph, Culture Northern Ireland and BBC Radio Ulster.