“The Face of Love” opens Friday at Sundance Cinemas. PG-13, 1;32, two stars out of four.

It would seem that all you would have to do is point a camera at Annette Bening and Ed Harris and you’d have yourself a movie. Both actors seem incapable of seeming inauthentic on screen — Harris has been a charimsatic character actor for 30 years now, while Bening creates satisfyingly complex women nearly every time she’s on screen. Just put them at a dinner table, give them something to say, and they’re off.

But Arie Posin’s “The Face of Love” saddles the actors with a plot contrivance so unbelievable that the actors seem to have to work around it. What should have been a thoughtful late-middle-aged love story instead becomes a game to see how long the film can handle its contrivances before they blow up in its face.

Bening is Nikki, a Los Angeles widow quietly nursing her grief at the drowning death of her husband Garrett (Ed Harris) five years earlier. After five years, Nikki isn’t a wreck, but Bening deftly shows us how she still carries that absence around with her every day. (Against these subtle shadings, that Nikki refuses to swim in her backyard pool seems like an even clunkier plot device than it already is.)

Nikki and Garrett loved to wander the Los Angeles County Museum of Art, and on one visit there, Nikki sees him again. Or rather, she sees a man who is an exact lookalike of Garrett, also played by Ed Harris. Fascinated, she stalks him a little and finds he’s a college art teacher named Tom. Mystified and thrilled, Nikki sidles into Tom’s life, and the two start a relationship, Tom completely unaware of his resemblance to Nikki’s late husband.

This is the point in which you think “The Face of Love” could have gone anywhere, could have turned into a magical realism-inspired love story, or backgrounded the doppelganger plot and focused on Tom and Nikki’s relationship. Instead, Posin and co-screenwriter Matthew McDuffie opt for a kind of Vertigo Lite, as Nikki dresses the oblivious Tom up in Garrett’s old clothes, even (and incredibly) takes him on vacation to the oceanside spot where Garrett drowned. This is deeply creepy behavior by Nikki, and yet the film doesn’t have the courage of its convictions to follow through on that, never sure whether Nikki is being delusional, or simply finding an unorthodox way of dealing with her grief.

It’s all very hard to swallow, and rather than getting emotionally invested in these characters, we just wait for that last narrative shoe to drop. Harris and Bening do their very best to sell it; Harris creates a very believable character in Tom, a faded ex-bohemian  looking for something lasting in the winter of his life. But mostly we just feel sorry for him. And Bening, when she simply tells her daughter (Jess Weixler), “I need him,” almost makes us believe she’s doing what a lonely woman would do, rather than something a screenwriter would dream up. Almost.