“That was a good ending!” declared the man sitting in front of me as the lights went down at the conclusion of the Jungle Theater’s Wednesday night performance of The Night Alive. I wasn’t sure, though, that I agreed with him in either sense of that judgment.

If he meant it was good in the sense of being happy, I think he might have missed evidence in Conor McPherson’s script that it might not stay happy for long. If he meant, alternately or additionally, that it was good in the sense of being a satisfying dramatic resolution — well, that’s more difficult to argue, but to me, it was an ending that confirmed a fairly simplistic interpretation of characters who weren’t too complex to begin with.

The play begins with a premise that could have come from a José Feliciano song — though it’s set in Ireland. Tommy (Stephen Yoakam) is a middle-aged man who’s separated from his wife and teenage children; he rents a room in the house of his widower uncle (Martin Ruben). He brings Aimee (Sara Richardson), a young woman, home to clean up and rest up after he sees her being beaten by her boyfriend.

The show’s warmth is immediately apparent. Tommy seems to be a genuinely nice guy, despite the shabby state of his living quarters and his marriage. Aimee has a million-dollar, if lopsided, smile; and as information about her past emerges, their relationship starts to have shades of a working-class Pretty Woman. The world’s oldest redemption story?

Well, yes and no. I would have been happy to follow that conversation between Tommy and Aimee all night long, but instead McPherson hops us into the next day as we meet Tommy’s business partner — in the sense that they do odd jobs together — Doc (Patrick Bailey). Doc is an affable, simple guy who cherishes Tommy’s friendship; neither of the two, after all, seems to have any other friends. Initially suspicious, Doc quickly warms to Aimee — but unfortunately he’s the one who answers the door when Aimee’s wild-eyed boyfriend (the lanky Tyson Forbes, who seems to be able to cross the entire stage in a single menacing stride) comes knocking.

This is in many ways a bleak scenario, but McPherson and director Joel Sass (who also designed the wonderful set) orchestrate such sympathy for the core trio of Tommy, Aimee, and Doc — each a plucky survivor, in his or her own way — that we believe happiness is possible for these characters, and we root for them. They’re so appealing, and the show is full of so many amusing details (like the outsize sneakers Aimee presumptively steals to present to Tommy) that by the time the Christmas lights are being hung, we start to believe that there’s potential for a happy ending despite there being enough tragedy to make Uncle Vanya look like Full House.

Though there’s a lot to like about The Night Alive, it goes off the rails about halfway through, when it becomes clear that the show will be dominated by gothic plot twists rather than meaningful character development. Tommy and Doc are lovable losers who just seem to be trying to catch a break; whether they do or not doesn’t seem to be anything that’s up to them. Uncle Maurice, whose grief is as bottomless as his pocket flask, is someone we figure out pretty quickly and that’s that. Aimee’s boyfriend Kenneth is simply a monster.

That leaves Aimee as the most potentially interesting character — but between Tommy’s shambling shenanigans and Kenneth’s stagey thundering, we never learn much about what makes her tick. She does make a decision (or two, or three) that might surprise us, but McPherson largely leaves the logic behind each decision implied. The story of Aimee, then, becomes a sad one that’s been told many times — whereas she could have been a more distinctive character. Richardson’s magnetic performance suggests depths that are never plumbed.

McPherson’s complex and entertaining play The Seafarer was presented at the Jungle in 2009; and at the time I wrote that it was “downright subversive” of the company to produce “a Christmas story that suggests that maybe the poor are just as messed up as the rich.” With The Night Alive, we still find ourselves among “the surplus population” — but this time around, we’re reminded why the virtuous and downtrodden Cratchits aren’t particularly interesting characters. Still, God bless ’em, every one.

– Jay Gabler