The triangle express

“I’m so ready to be happy,” Helena Bonham Carter’s wild and crazy Dinah says, and she really means it. Unfortunately for her -- but not for us -- she is very much in the wrong movie.

For “The Heart of Me,” in which she co-stars with Olivia Williams and Paul Bettany in a traditional romantic triangle, is a genteel, old-fashioned weepy of the multi-hanky variety, in which the well-bred characters experience every emotion imaginable except lasting happiness.

But what is catastrophic to Dinah and her cohorts will be catnip to fans of the kinds of high-tone romantic melodramas the British used to do in the 1940s, films like “Random Harvest” and “Waterloo Bridge,” in which everyone suffers, suffers and suffers some more for love.

“The Heart of Me” is not truly in that league, but it is quite well done, with a fine cast finding time between tears, anger, deception and recriminations to do some surprisingly strong and affecting acting. Directed by Thaddeus O’Sullivan and written by Lucina Coxon, “Heart” is adapted from “The Echoing Grove,” a 1953 bestseller by Rosamond Lehmann that was apparently loosely based on her own affair with British writer C. Day Lewis.

“Heart” takes its characters through a dozen eventful mid-20th century London years, starting them out in the white tie and tails glamour of the 1930s and moving tearfully into the world war and the blitz. Central to the film are two sisters, Bonham Carter’s Dinah and Williams’ Madeleine, siblings so diverse, so appealing in quite different ways, that if they could be combined they’d probably make an ideal human being.

Madeleine is a successfully married young mother, a clever woman happily wed to handsome Rickie (Bettany), who does some unspecified financial work in the city. She oversees “the smartest house in London” and is initially engaged in trying to find a suitable man for her sister. That would be Dinah, the passionate artistic iconoclast who reads William Blake and walks off in rainstorms without caring whether she gets wet. Not wanting to make a fuss, Dinah agrees to marry a dolt she doesn’t really care about when Rickie, of all people, tells her she mustn’t.

Yes, you’ve guessed it: Rickie and Dinah are hopelessly smitten and soon can’t keep their refined hands off each other. Hardly the culmination of “Heart’s” plot, this is its merest beginning, as all kinds of increasingly unexpected and precipitous turns dog the footsteps of this troubled trio.

Though nothing if not traditional in broad outline, “Heart” has a number of things going for it, starting with a handsome look and an interesting structure, which jumps ahead in time and then backtracks, filling in the gaps.

The film also has the great advantage of actors who take their parts completely seriously, knowing when to play things discreetly and when to take full advantage of the moments of true emotion. The boyish Bettany, best known for being imaginary in “A Beautiful Mind,” is convincingly torn between the two sisters, while the two starring actresses do a remarkable job of conveying not only romantic longing but also sibling rivalry. For “Heart” turns out to be as much about the competitive relationship between sisters as it is about love lost and found.

Perhaps “The Heart of Me’s” greatest success is the way it avoids turning any of its characters into villains. They all act badly at times, but we feel for them just the same; they never lose our sympathy. Weepy or not, that’s an accomplishment any kind of film can feel proud of.

*

‘The Heart of Me’

MPAA rating: R, for some sexuality.

Times guidelines: Adult subject matter, some genteel nudity.

Paul Bettany...Rickie

Helena Bonham Carter...Dinah

Olivia Williams...Madeleine

Eleanor Bron...Mrs. Burkett

Released by ThinkFilm. Director Thaddeus O’Sullivan. Producer Martin Pope. Executive produceres David M. Thompson, Tracey Scoffield, Steve Christian, Keith Evans, Paul Federbush, Sebnem Askin. Screenplay Lucinda Coxon, based on “The Echoing Grove” by Rosamond Lehmann. Cinematographer Gyula Pados. Editor Alex Mackie. Costumes Sheena Napier. Music Nicholas Hooper. Production design Michael Carlin. Running time: 1 hour, 36 minutes.

In selected theaters.