“Third Person” opens Friday at Sundance Cinemas. R, 2:17, one and a half stars out of four.

Man, it’s so hard to be a famous writer. Holed up in a swanky Parisian hotel suite, occasionally pecking away at the laptop, with only occasional visits from Olivia Wilde for company. Seriously, I don’t know how I do it.

Oscar-winning writer and director Paul Haggis (“Crash”) certainly means to be hard on himself with his new film ‘Third Person,” whose main character is a past-his-prime novelist who uses the people in his own life in his fiction. But, when you cast Liam Neeson as your on-screen avatar, you’re not exactly raking yourself over the coals.

Neeson plays Michael, a writer who has come to Paris with a particular set of skills — drinking, sleeping with other women, and occasionally writing down what he or other people say and calling it fiction. He flies over his mistress Anna (Wilde), a less successful writer, from the States for company. They have sex, fight, have sex, fight, have a little less sex, fight a little more. There’s very little chemistry between the two characters on the page (“Love. You don’t even know what the word means.”) or on the screen. Wilde and Neeson are appealing actors, but she keeps flashing hot and cold depending on the whims of the script, while he just looks like he wants a nap.

Their storyline is fairly inert, so Haggis weaves in two other, seemingly unrelated storylines, “Crash”-style. In New York, a hotel maid (Mila Kunis) is locked in a bitter custody struggle with her ex, a famous painter (James Franco). She’s been accused of child abuse against their son, and while Haggis wants to keep us in suspense over whether she’s guilty or not, she’s just not a very interesting character either way.

The third storyline tries to make up for the stasis of the first two with too much plotting. Adrien Brody is a corporate spy in Rome to steal some fashion designs who, in a frankly unbelievable set of events, gets himself entangled with a Romanian beauty (Mora Atias) trying to pay for her daughter to emigrate illegally into the country. In contrast with the morose plodding nature of the rest of the film, this storyline has broadly comic touches (such as a running joke about tiny Italian cars) and a thick coat of melodrama, as when Brody meets the villainous human trafficker who has the daughter.

“Third Person” goes on for well over two hours, until Haggis tries to pull all his narrative strands together in a highly unsatisfying finale. I actually liked the much-maligned “Crash,” which could hide the occasional thinness of its characters because of their sheer number and the rich cross-cutting and narrative reverals. It was a screenwriter’s movie.

So is “Third Person,” but with fewer characters and very little plotting, the seams in his characterizations are that much more visible. There are some truly silly plot revelations here, and Haggis has never met an emotional moment he couldn’t oversell with a swell of ear-splitting strings.

“Third Person” is at heart about how writers mine their own lives (somewhat ruthlessly at times) for their material. In that case, Haggis may need a more dramatically interesting life to work from.