Little John Nee is an unlikely gangster as he makes his entrance in "The Derry Boat," his one-man show being presented by the Keegan Theatre at the Rosslyn Spectrum. Cued by a dissonant, crunchy electric guitar chord, Nee, as Shugie O'Donnell, crashes through the door of a corrugated metal shack in a rumpled black suit and tiny sunglasses, waving a gun and toting a large suitcase.

It's the kind of opening you'd expect from a low-budget independent film, not from an imported Irish show billed as a fable about three generations of Irish immigrants in Scotland. But "The Derry Boat" is full of pleasant surprises, the chief one being Nee himself--a deadpan presence who guides us through the brutal hardships and misadventures of the O'Donnell clan. Against all odds, the show turns out to be both a cultural chronicle and a whimsical caper comedy.

Don't let his name fool you: There's nothing cute about Little John Nee, even when he's singing an overblown ode to wood lice. "I used to be a wood lice one time meself," he says, and you get what he means--a down-and-out survivor. Singing what amounts to an Irish parody of Bruce Springsteen ("You and me and a tank full of petrol," he croons), Nee, who wrote the story and the songs, steers clear of yearning and sentimentality. In fact, there's not a sentimental note to be heard all night.

That's something, since Shugie O'Donnell passes the roughly 75 minutes waiting for his girl to meet him at this run-down shack (designed by director Paraic Breathnach) by recounting the tragedy-filled, multigenerational tale begun by his grandfather's flight from Donegal to Glasgow on a smelly, crowded cattle boat departing from Derry. The family house in Donegal was torched by soldiers. John O'Donnell (Shugie's grandfather) took up coal mining in Glasgow, where one of his daughters died and his wife went insane. Shugie's dad beat his wife ruthlessly until she died of tuberculosis. And so on.

The storytelling style deployed by Nee and Breathnach--aided by John Hoban, who provides a soundtrack with guitar, keyboard and drum--is vivid and economical. With a change of hats Shugie becomes his grandfather; he creates the boat by arranging a length of rope and a few crates; poking his head through one of the large metal drums on the stage he's John O'Donnell in a mine shaft. Nee moves through all this with speed and a stone face. Even his whimsies--like getting the audience to moo in unison, or spritzing the front rows with water during a choppy time on the Derry Boat--have a dark undercurrent. It's as if Shugie's blank expression is telling us, don't trust the fun.

That, of course, gives a luscious irony to Nee's folksy songs and low-key jokes. But though the material and the performance have a kind of sober purity, you never get the sense that Shugie is a brooder. Even in the midst of such a bleak assembly of incidents, the show has an oddball joie de vivre. Near the end, Shugie complains about the "victim mentality" that, in his opinion, plagues previous Irish generations, and he sounds right in character when he says it's a legacy he means to avoid.

Which brings us to the gun and the suitcase and the unlikely final chapter in the O'Donnell saga. Like the rest of the show, it's full of black developments and imaginative gallows humor--a perfect capper for this unexpected little epic.

The Derry Boat, written and performed by Little John Nee. Songs by L.J. Nee. Directed by Paraic Breathnach. Lighting and sound design, Jim Faulkner; music direction, Fergal Gallagher. Through Jan. 29 at the Rosslyn Spectrum, 1611 N. Kent St., Arlington. Call 703-757-1180.

CAPTION: Little John Nee spins tales of the bad old days in "The Derry Boat."