“Joan of Arcadia” is really two shows stitched awkwardly together. The first–the good one–is about Joan, her run-ins with God (he wants her to apply herself more) and her relationship with her two siblings: 15-year-old science geek Luke (Michael Welch) and paraplegic older brother Kevin (Jason Ritter), a dreamboat who lost the use of his legs in a car accident. When God introduces himself to Joan after their bus ride, she’s skeptical. But he convinces her of his divinity by ticking off a list of things only God could know, like how her parents met, that she likes salt on her cantaloupe and is afraid of clowns. And in that corduroy coat, God looks hot. “Is it weird that I kinda have a crush on you?” she asks. God smiles. “I won’t look like this the next time,” he says. Hmph. Deities.

The show’s crop of gifted young actors bounce off each other like charged ions, and creator Barbara Hall is a natural with sharp, “Gilmore Girls”-y banter. In fact, the show seems better suited to the WB than the adult-minded CBS–except for the moments when Hall shifts focus to Joan’s father, the Arcadia chief of police (an over-earnest Joe Mantegna), as he gumshoes through violent murder mysteries. This is the lousy, second show, and it plays like table scraps from “CSI.”

Dialing back the cop stuff, or cutting it out entirely, would make “Joan of Arcadia” more cohesive and more fun. But it wouldn’t help the fact that it’s on the wrong network. CBS clearly signed up Mantegna–and Mary Steenburgen as Joan’s mother, who’s going through a spiritual crisis after her son’s accident–to class up the joint and bring in adult viewers. But CBS’s real challenge is going to be persuading teenagers to watch a network that hasn’t offered them much beyond “Survivor” in the past. Hey, God, a little help?