Motion pictures tend either to tame the more strenuous efforts of distinctive actors or to permit those of much lesser artistic means to coast through to acceptable results. Hambone histrionics and a commanding presence are restricted by the technical requirements and opportunities of movie production and the pervasive power of the director.

Cherie Nowlan’s Introducing the Dwights allows Brenda Blethyn a lot more latitude than is usual, but that’s mostly because so little else is going on much of the time. In some scenes it’s not much of a contest between her performance and the script and direction. Blethyn rises above the movie’s flattish planes.

An Australian production, Introducing the Dwights is concerned with the enmeshing perils of mother love. Blethyn is Jeanne, a bawdy, part-time, cut-rate comic, a divorced mother of two who works during the day in a factory commissary. The movie depicts, in its desultory way, the hesitant development of her elder son Tim’s reaching for independence via a romance with a willing girl, and Jeanne’s insidious, mean and frightened attempt to derail the couple.

Some of this is modestly amusing and affecting, but there’s only barely a dramatic arc and very little embroidery. Khan Chittenden is winsomely winning as Tim, and he even holds his own in a couple of scenes where Blethyn does simmering resentment or raging recrimination. But the movie has begun to fold its tent and withdraw from competing with Blethyn long before we get to the unearned resolution.