It is December, Christmas is coming and Pete (Paul Rudd) and Debbie (Leslie Mann) both find themselves celebrating their fortieth birthdays. She’s not thrilled about this, of course, forgoing the couple’s usual joint party in favor of letting her husband celebrate on his own.

Leslie Mann and Paul Rudd in This is 40 © Universal Pictures

But before the fete even happens the longtime marrieds are having problems. They spend more time arguing with one another than they do expressing their love. Pete is conflicted whether or not he should tell his wife that his struggling record label is underwater, putting their financial stability in immediate jeopardy. Debbie has been keeping the fact she’s been meeting with her estranged biological father Oliver (John Lithgow), a man she hasn’t seen in something close to a decade, from her husband, not positive this is information he needs to know.

These are only the basic undercurrents running underneath Judd Apatow’s This is 40, the writer/director returning to a pair of Knocked Up secondary characters giving them the spotlight as they navigate dual midlife crisis and try to reconnect and cement their love even as their world seemingly spirals out of control. It’s Scenes from a Marriage, the slightly more conventional and comedic version, a movie filled with numerous bracing emotional insights even if it doesn’t always know exactly what’s best to do with them.

Not to say this sort-a-but-not-really-a-sequel isn’t without its charms, it’s got tons of them, not the least of which are the performances by stars Rudd and Mann. Both show a complete fearlessness to strip themselves bare, showing their naked innards as they explore tough, exacting material while at the same time trying to do it with a bit of a smile and an ounce of quirky sarcastic humor. They find light in the dark, laughs in the pain, mining the depths of a complicated marriage in ways that feel natural and true.

But the episodic nature and the sheer length of the motion picture can oftentimes work against the material. At 134 minutes the movie can’t help but drag, subplots involving Debbie’s boutique clothing store employees Desi (Megan Fox) and Jodi (Charlyne Yi) as well as Pete’s record label cohorts Ronnie (Chris O'Dowd) and Cat (Lena Dunham) cute in and of themselves but not adding near as much to the proceedings as I imagine Apatow feels they do. Every time I found myself becoming captivated what was going on up would pop a supporting player doing something silly taking me out of the moment, putting me on frustrated edge more than they did anything else.

Yet when the movie works it does so splendidly. The heart of the picture, the evolving nature of Pete and Debbie’s marriage, how they relate to their children Sadie (Maude Apatow), 13, and Charlotte (Iris Apatow), 8, the way they deal with their respective fathers, the distant and uncertain Oliver on her side, the gregarious if needy Larry (a sensational Albert Brooks) on his, all of it comes together in a way that bristles with touching authenticity. You get what they are going through no matter what you’re age, watching them fall apart only to emotionally rebuild and reconcile as blissful a sequence of events as any I could have hoped for.

I just wish it held together, didn’t so often go off on pointless tangents involving little of anything close to important. The up and down nature of it all put me at continual unease, and more often than not I found myself getting angry at Apatow for losing his way while crafting a story filled with sensational heartbreaks, joys and emotionally resonate upheavals. The filmmaker knows what he’s talking about here and isn’t slightly afraid of going into some exceedingly dark places, and while I applaud him for doing so I just as vociferously castigate the Funny People auteur for including so much superfluous nonsense.

Maybe I’ll like This is 40 more the second time around, maybe I’ll respond to all of Apatow’s secondary storylines and find them more fulfilling when I get the opportunity to examine them again. Right now, however, as much as I loved large portions of the film on the whole the stuff that doesn’t work is leaving too much of an ill aftertaste for me to be able to embrace it nearly as much as I’d like to. The movie does have its merits, more than its fair share, and I certainly wouldn’t begrudge interested parties from taking a look; I’m just not positive they’re going to fall in love with the whole near as much as they do some of the individual pieces.