Starring Alan Rickman, Sigourney Weaver, and Carrie-Anne Moss. Rated PG.

In Snow Cake, Alan Rickman and Sigourney Weaver offer a master class in what old pros can do with so-so material. That may sound like faint praise, but they do enough to bring some profound insights to the tale of a lonely man and an even more isolated woman.

Here, Truly, Madly, Deeply actor Rickman plays Alex Hughes, a taciturn Englishman in Canada on a vaguely defined personal quest. He shows up south of Wawa, Ontario, in a rental car and proves to be both a white knight and an agent of tragedy to a talkative young woman (A Problem With Fear’s Emily Hampshire) looking for a lift. This kind of trouble seems to dog Alex, and he feels obliged to find the girl’s mother and explain things—to explain himself, in a way.

The fact that the mother, Linda Freeman (Weaver), is a high-functioning autistic offers both a challenge and the key to his mission. And for one reason or another, he ends up staying with her for a while. This odd-couple pairing is an indication of how the cards are stacked in this Canada–U.K. production, which constantly threatens to slide into the self-consciously ridiculous while affording the cast ample opportunity to make the effort worthwhile.

While Linda scuttles about—going gaga over shiny things and fiercely enforcing her compulsions in the kitchen, where Alex isn’t allowed—Alex reexamines his notions of sufficiency. He also takes increasingly frequent walks with Linda’s dog, seldom getting farther than next door, where Carrie-Anne Moss is similarly impressive as a promiscuous neighbour—a stroke of luck for a fellow who has of late been in prison, and not just the metaphorical kind.

The problem for us, if not for Alex and the dog, is that screenwriter Angela Pell doesn’t seem to have thought very carefully about who these characters might truly, madly, deeply be, beyond their convenience as discussion starters in a playlike study of human isolation. There’s always something dubious about using dead children as a device to bring lonely people together. And it doesn’t help when everyone is asked to stand around numbly—like Callum Keith Rennie, as an accident-prone truck driver—pleading for expiation and better dialogue.

Fortunately, Welsh-born director Marc Evans puts his faith in the actors and not in the script, allowing them to invest more humour and complexity than appears on the page. The result, much like the title dessert Alex whips up for the easily pleased Linda, is prettier than it is digestible. But sometimes sparkles are enough.