Dark humor on the Emerald Isle

Not that Billy Claven, the title character, splendidly played by Tadhg Murphy, can see much variety. To Billy, a youth of 17 or 18, there’s no place like home . . . when it comes to stifling the spirit. For lack of anything better to do, he spends much of his time staring at cows.

Left an orphan when his parents drowned under mysterious circumstances, Billy has been raised by a pair of kindly, eccentric storekeepers, Eileen (Dearbhla Molloy) and Kate (Ingrid Craigie). He is severely disabled, with a deformed right foot and a right arm that dangles uselessly at his side, which earns him the nickname “Cripple Billy’’ among his fellow island inhabitants. They include JohnnyPateenMike (Dermot Crowley), the island gossip, and Slippy Helen (Clare Dunne), the volatile young woman on whom Billy has a crush.

When an American film company arrives to make a documentary at a nearby island (an episode inspired by Robert Flaherty’s 1934 movie “Man of Aran’’) Billy seizes on the chance at least to try to break free and forge a new life for himself.

None of this makes “The Cripple of Inishmaan’’ sound funny, does it? But it is. McDonagh finds a vein of dark comedy in the brutal directness of the island’s inhabitants, who are not necessarily mean-spirited but lack any of the usual social filters. “I’ve heard me mammy was a beautiful woman,’’ Billy says to his physician. The doctor replies: “No, no, she was awful ugly.’’ Billy: “Was she?’’ Doctor: “Oh, she’d scare a pig.’’

The playwright also has mordant fun with the oblivious, skewed logic of his characters’ quirky digressions: the murder of a goose and a cat; the loose morals of the (unseen) daughter of Jim Finnegan (also unseen); the obsession with telescopes that transfixes Helen’s brother, Bartley (Laurence Kinlan); Kate’s habit of talking to a stone when under duress.