In her directorial debut, Jennifer Westfeldt revisits familiar terrain with new characters leading the way. Though Adam Scott is terrific as her potential romantic partner, the trip is disappointing, lacking the fresh insight that Westfeldt brought to her previous efforts as writer and star.

Westfeldt broke out with ‘Kissing Jessica Stein’ (2001), which she wrote with Heather Juergensen, based on characters they created for the stage, two women who become friends and then start moving toward a sexual relationship. The comedy was sharp, the drama was effective, and significant issues were addressed in a realistic manner.

Five years later, Westfeldt went “solo,” so to speak, with ‘Ira & Abby,’ set in a “charming, alternative romantic-comedy universe,” as I described it, “a world in which a warm, friendly butterfly of a woman can disarm an angry subway robber and talk the passengers into taking up a collection for the thief.” Her character proposes marriage to an extremely neurotic man after six hours of intense conversation; the balance of the film tracks the course of their relationship, a classic tale of “opposites attract” that director Robert Cary kept moving at a brisk pace. Even so, by the third act the material felt stretched beyond its limits and the film began to sag, a structural issue shared by ‘Kissing Jessica Stein.’ In both cases, the goodwill built up through the earlier stages was sufficient to carry the stories through to their conclusion.

The goodwill and momentum is missing from ‘Friends With Kids,’ which follows a similar pattern by starting with bright, comedic patter before descending into more straightforward domestic drama. Westfeldt plays Julie, who lives in the same building as her longtime best friend Jason (Adam Scott). They’ve been friends so long that they feel entirely comfortable sitting in bed with anonymous lovers asleep at their sides, calling each other in the middle of the night to joke and make plans to get together.

They are good friends with two couples, the newly-together Ben (Jon Hamm) and Missy (Kristen Wiig), who are in the ‘incredibly horny’ phase of their relationship, and the newly-pregnant Alex (Chris O’Dowd) and Leslie (Maya Rudolph), who are resolved not to act like all other parents.

Four years pass. Jason and Julie are still single, while their friends are now, well, friends with kids. Well into their 30s, Jason and Julie question whether they’ll ever find that ‘special someone,’ and Julie is conscious that her biological clock is running out. An off-hand comment by Jason leads to their decision to have a baby, and then raise the child, together, even though both deny any physical or sexual attraction to the other.

Once they become parents and begin spending even more time together, their feelings ebb and flow, as does their relationship with their friends. Naturally, their friends are also changing as the years pass, their respective relationships becoming either stronger or weaker.

The set-up is achingly familiar, and though the opening sequences are packed with one-liners, the observations merely echo what single people have noted about their “friends with kids” for the past two or three decades. Without a new angle, the material feels stale, and the stodgy pacing lingers too long over situations that don’t merit a closer look.

Scott very nearly saves the film single-handedly, milking the humor (and the pathos, when appropriate) out of every line reading and reaction shot, deftly adjusting his performance to match the setting and the other characters. Westfeldt is not his equal as an actor, which throws the balance off a bit, but not so seriously as to be overly distracting.

The supporting performances by Hamm, Wiig, Rudolph, and O’Dowd are fine, as are turns by Megan Fox and Edward Burns, who play thinly-disguised versions of their public personas in their roles as new lovers for Jason and Julie, respectively.

Disappointing in large part due to the high standard established by Westfeldt in her previous films, ‘Friends With Kids’ could strike a chord with people of a certain age, who may find meditative food for thought. It’s not a bad movie, by any means, and Adam Scott alone makes it worth seeing out.

‘Friends With Kids’ opens in Dallas today at Landmark Magnolia.