I feel I would have liked “Admission” better if I had known going into it that it wasn’t going to be funny. So I am preparing you accordingly to save you the trouble I had: “Admission” stars comedic actors Tina Fey and Paul Rudd but is not a comedy. So don’t waste any time waiting for giggles. There are none on deck for you.

With our expectations adjusted, let’s dive in. Tina Fey plays a competent, committed Ivy League admissions officer living a carefully managed life with a stuck-up professor. In an amusing early scene (OK, it was amusing but not funny) we quickly get a sense of their lack of passion, and it’s not a huge surprise when he ends it in a businesslike, brotherly fashion. His abrupt and humiliating abandonment of her is supposedly an ongoing source of distress for her character, but the idea that she really cares is unconvincing.

She keeps encountering him as he pursues a new and possibly fuller life, right at her lowest moments, but this is just a running joke, not a character motivation. What does motivate her is meeting a brilliant but weird student at a woodsy alternative high school, who, it is explained by his teacher, is most likely the son she put up for adoption when she was in college. Paul Rudd plays the teacher, himself an intentionally rootless citizen of the world, dragging his own adopted son through a peripatetic existence.

Both Rudd and Fey have upbringings from which they are rebelling; Rudd’s is one of stifling privilege while Fey struggled with a decidedly anti-nurturing single mother. Portrayed by Lily Tomlin, the role of the mother was by far the most interesting, unusual and intriguing aspect of this film. Tomlin was shockingly callous; when she explains that she doesn’t feed her dogs because they’re animals and need to fend for themselves, we get a pretty clear picture of Fey’s childhood.

Tomlin achieved what the rest of the film rarely did; a good mix of humor and pathos. She was unbelievably mean, but also believable. She was utterly, memorably savage, and it was kind of a revelation to see her like that. For most of the rest of the story, the viewer has trouble figuring out what’s real and meaningful. The result for me was I couldn’t believe how sad this story was actually going to turn out to be, and was it intended, I couldn’t make sense of it, but not in a good way.

Another thing I didn’t know before I watched this was that it was directed by Paul Weitz, who created a marvelous mix of humor and drama in “About a Boy,” a perennial favorite. Of course, that was based on a novel by Nick Hornby who, when it comes to a proper laughs/tears mix, pretty much, well, wrote the book. Not so with “Admission,” although apparently also based on a novel, which fails to consistently strike the right notes. It’s rarely funny enough to be funny, or affecting enough for the situation we find ourselves watching. The results are unsatisfying.

It pains me to lay this problem at the feet of the leads, of whom I am, independently, quite fond. They are both likeable, and I’ll even grant them some chemistry, but their characters’ situations become too serious for the performances they deliver. I’ll blame the writing. Rudd’s character, especially, just acts too abruptly in service of the plot twists, and, as I find myself repeating, I just didn’t believe it.