The low-budget but heartfelt indie “A Little Help” gets off to a fine start: Laura (Jenna Fischer, “The Office”), a dental hygienist, and her husband Bobby (an effective, brittle Chris O’Donnell), a real estate agent, have drifted apart to the point of resentment.

She accuses him of working too many hours and possibly cheating on her. He complains she’s let herself go, she’s drinking too much and she’s not someone to whom he’s eager to come home.

Caught in the middle is their 12-year-old son Dennis (Daniel Yelsky), who is surly and withdrawn in the usual manner of children of bickering parents.

In those early scenes, writer-director Michael J. Weithorn crafts an intriguingly realistic look at a marriage that gradually crumbled when no one was looking, and you wonder if there’s any hope for this couple, who obviously still love each other, to get their groove back and become a family again.

But then, in an ill-conceived twist that changes the entire tone and theme of the movie, Bobby drops dead of a heart attack, and Laura is left to pick up the pieces.

“A Little Help,” which is set in 2002 to allow for some queasy references to Sept. 11, intends to be a dramatic comedy about human resilience and the way in which we force ourselves to push forward even after life has dealt us an impossible hand.

Laura’s mother (Lesley Ann Warren) and sister (Kim Coates) are constantly on her back, pushing her to file a suit against the doctor who misdiagnosed Bobby’s chest pains as an anxiety attack.

Dennis, who had a strong attachment to his father, isn’t any easier to deal with, lashing out in ways that create more headaches for the beleaguered Laura.

Filmmaker Weithorn obviously has a sharp sense of humor – a parrot in the dentist’s office in which Laura works, which is intended to be a calming presence for patients, is always shrieking “Earthquake!” – but “A Little Help” doesn’t settle for the dark comedy it should have been.

The movie wants to be an exploration of family ties and the various ways in which the people we love respond in times of crisis, but the drama is unconvincing, the characters are ill-defined, and Fischer, so good on “The Office,” seems a bit incomplete without Jim at her side.