To theatergoing audiences, Sandra Hardy is known best for directing musicals. And she’s a cinch at comedy. But with a new production of Judith Thompson’s searing drama “The Crackwalker” at the University of Maine, Hardy isn’t singing or laughing. She’s getting right up in your face, poking you in your chest and saying, “Hey, pay attention; you might learn something.”

Thompson wrote “The Crackwalker,” playing this weekend in Hauck Auditorium, nearly 20 years ago while working as a social worker in Ontario. She focuses on four members of the underclass there — one is mentally retarded and coupled with one who is dim-witted, and the other two, who are also coupled, are violent castoffs from an unloving society.

Plot is not the biggest factor in this two-hour dissection of those who have, as the title suggests, fallen through the cracks. The couples fight, laugh, drink, party, have sex and eat. Routine enough, really, for young people.

Add to that the frustrations of poverty, the perversions of neglect and the calculations of a worn-thin, bureaucratic mental health system, and you have a play that hardly qualifies as light entertainment.

These are people whose vocabularies draw heavily on four-letter words that begin with “f,” “c” and “s.” They hit each other. They lie. They are loud and crude and angry. They even kill. But more than the system that nudged them into this dark corner, these characters find a way to understand and have compassion for one another.

Yesterday, after a noontime matinee, two college students looked visibly shaken walking out of the theater into sunlight.

“That was too –,” the first one said.

“Yeah –,” the second one answered.

“Right,” the first one agreed.

Clearly, “The Crackwalker” is not a first-date kind of play. Hardy, who teaches acting at UM, makes no excuses for its scabrous quality.

“I had a group of students I thought could handle it,” she said in a recent phone conversation. “You have to challenge actors. That’s all there is to it. You can only do musicals so long. This is a way of saying we’re not all about creating fun for you. We’re about provoking you.”

And provoke they do. The leads in the show put on the performances of their college careers. The two women — Misty Dawn Jordan and Kristen Williams — have the most commanding presences onstage.

Jordan, who plays the mentally retarded Theresa, isn’t always easy to understand, but what she lacks in enunciation, she makes up for in clarity of character. Her performance is bold in that she isn’t afraid to be funny and then to turn around and be gut-wrenching.

The men — Christopher Ashmore and Andrew Lyons — are no less effective, but their characters are less compelling and sympathetic. Henrique Fontes makes charismatic cameo appearances as The Man, a street person who, in his seedy silences, screams out: If you think these people got it bad, look at me.

A technical crew made up primarily of students has stripped away any hint of prettiness. The stage is bare except for black wooden set pieces and screens that do little to shield us from harsh realities. Lighting, which generally combines bright whites and eerie reds, suggests no real chasm between holiness and horror.

There are moments in this production that might be stronger with a more mature cast. Yet there’s no mistaking these student actors are a collective tour de force, both exhaustive — and exhausting. Violent scenes are not gratuitous. Neither are the tender ones. If anything, the only gratuitous scene comes at the end when a crucifix is projected onto one of the screens.

It’s true: “The Crackwalker” is not a family play. And it may not be for everyone, even if you are a serious theatergoer. It’s downbeat, hard to watch and overly long. Some people are bound to walk out. (They certainly have at other venues.) But “Crackwalker,” in all its raw brutality, carries with it the power to sensitize those who haven’t fallen through the cracks. It won’t leave you with a song in your heart, but it will remind you that you have a heart.

Maine Masque will present “The Crackwalker” 7:30 p.m. Oct. 22-24 and 2 p.m. Oct. 25 in Hauck Auditorium at the University of Maine. For tickets, call 581-1755.