Through five seasons of soap opera twists on the television spy series “Alias,” Jennifer Garner perfected the art of reacting to shocking revelations. “Catch and Release,” a misshapen mix of comedy and drama, is all about her character’s reactions to awkward secrets. Bereft Gray Wheeler (Ms. Garner) learns that her late fiancé, Grady, was apparently a) a millionaire, b) someone’s sugar daddy, and c) someone’s actual daddy.

That’s no spy-game double cross, but it’s up there. For the opening sequence, a funeral reception that should have been a wedding, Ms. Garner contorts her usually determined features into a rubbery mask of grief. But Gray’s self-deprecating voice-over tempers these early moments, and the scene eventually finds her unwittingly eavesdropping on a bathroom quickie between two funeral guests.

Broke and brokenhearted, Gray moves in with Grady’s friends and housemates, Sam (Kevin Smith) and Dennis (Sam Jaeger). They’re decent guys and happy to see her through a tough time. But Gray is wary of another old buddy, Fritz (Timothy Olyphant), the funeral lothario, who is also lingering at the cluttered house.

The shaking off of gloom amid shambolic shenanigans suggests the sort of love, laughs, and pain movie that coops up families or friends in a house after someone’s death (usually during winter). It’s a tricky tone and situation for a first-time director to pull off, even if she’s a successful screenwriter like Susannah Grant. Ms. Grant has managed, adequately if at times unevenly, the disparate balancing acts in “In Her Shoes,” “Erin Brockovich,” and last year’s adaptation of “Charlotte’s Web.”

But “Catch and Release” is a whole other story. The film’s awkwardness does not result from grappling with tough subjects like the tainted legacy of a loved one or the nurturing of a new identity. Rather, Ms. Grant’s shaky film discards its juicy conflicts and complications, pretending to resolve tensions by simply forgetting them from one scene to the next. Gray’s recovery from grief receives equal treatment as bits of comic business, some underdeveloped subplots, and interchangeable moments of camaraderie.

Underwritten characters are both a casualty and a source of this patchiness. Sexual tension predictably pushes Gray into a fling with unshaven Fritz, but the situation makes less sense the more serious it gets because we know so little about him. (Mr. Olyphant, often at sea, looks as if he might bolt at any moment.) Gray remains a puzzle who seems to have no family or friends outside the house o’ guys. A promising bout with Grady’s combative mother (Fiona Shaw) points to harder themes of guilt and resentment, but, much like everything else here, it peters out.

The arrival of Juliette Lewis as the Other Woman, trolling for her monthly check, hardly seems to rock the boat. Maureen, an oblivious masseuse marinating in New Age and self-help speak but also remarkably down-to-earth, arrives with a scruffy, mischievous toddler in tow. Gray looks shocked (naturally). Shortly thereafter Maureen is apparently staying at the house and cooking dinner, and Gray bursts into a litany of charming, embarrassing confessions of the sort movie characters do to lay themselves bare.

Besides the trail of missing motivations, there’s evidence that a longer movie lies behind all this. Ms. Grant reportedly had to chop the film down from a three-hour version, and the high-volume soundtrack overlays, spotty location continuity, and pointless comic bits set to gamboling guitars seem to be papering over scars. Random technical noodling, like the arty double exposure for a love scene, suggests bartered concessions.

But the directorial decisions, whatever the circumstances, simply don’t allow characters to react to what’s happening. Ms. Garner’s wholesomely dutiful performance makes the lurches feel more pronounced, and the movie’s resolution of Gray’s predicament becomes an exercise. This works to Mr. Smith’s benefit, since his sensitive slacker hardly has an arc for the reeling story to fragment, but the tying up of romantic loose ends doesn’t spare him, either.

As ever, Ms. Garner’s alert presence and striking face command our attention like a beacon, but she fails to show much range, neatening up an emotional mess even when the movie would profit from a countervailing current. “Catch and Release” thus leaves open the question of Ms. Garner’s acting chops on the big screen (but might also suggest the viability of an odd-couple comedy with the freewheeling Ms. Lewis). Fans will find themselves left in the familiar position of having to tune in next time.