On its surface, “So Help Me Todd” is fairly straightforward. Based on creator Scott Prendergast’s own experiences, the new dramedy tells the story of high-powered lawyer Joan (Marcia Gay Harden) and her private investigator son (Skylar Astin) forging an unlikely partnership. Each episode follows a different case before the odd couple team inevitably catch the culprit and teach each other a valuable lesson. So far, so fitting for a CBS procedural. And yet there’s something deeply uncanny about “So Help Me Todd,” which pairs an aggressive perkiness with moments of drama that feel more forced than moving.

Todd and Joan spend the first few episodes sniping at each other in between finding clues. Once Todd proves that he’s a good enough private investigator to overcome his spotty past, he joins Joan’s office, where he locks horns with an uptight coworker Lyle (Tristen J. Winger) and ex-girlfriend Susan (Inga Schlingmann), neither of whom get much to do outside giving Todd other people to talk to besides his mother. At home, Todd’s sister Allison (Madeline Wise) occasionally gives the show a much needed dose of dry skepticism, though she also is only here to support her brother and mother’s leading stories.

Harden heightens the patrician obliviousness of Joan, who prides herself on being put together even while reeling after her husband (Mark Moses) suddenly left her. Give or take a dozen botched pop culture references, Joan wouldn’t be out of place as one of Diane Lockhart’s friendly rivals on “The Good Fight.” (Whether or not “So Help Me Todd,” which references a cuckolded mayor’s wife as “pulling an Alicia Florrick,” takes place in the extended “Good Wife” universe remains to be seen — and frankly, I’d love to see it.) Astin’s Todd, meanwhile, feels ripped straight out of “Psych” with his self-referential asides and exaggerated gaping at every new twist. Beyond this pair, many of the supporting actors also don’t seem to know what kind of a show they’re supposed to be in, which makes the cases of the week particularly hard to care about.

So even while “So Help Me Todd” has a decent setup, its clashing tones make watching the show a genuinely jarring experience. To the tune of a zippy score signaling hijinks, we learn harrowing details of cases involving murder and sexual assault. The series’ framework depends on Joan and Todd learning to get along, but their constant bickering and dripping disdain makes their detentes less than persuasive. If “So Help Me Todd” can land on a consistent approach to its premise, it might settle into something more balanced. If not, though, it’ll remain more confusing than truly entertaining.

“So Help Me Todd” premieres Thursday, September 29 at 9 p.m. on CBS.