If you crossed a private detective along the lines of Sam Spade or Jim Rockford with Harry Potter, you’d end up with the basic idea behind The Dresden Files, a new series airing on the Sci-Fi Channel starting Sunday at 9 p.m.

Based on the novels by Jim Butcher, it stars Paul Blackthorne as Harry Dresden, a Chicago private eye who is also a wizard. (He advertises as both in the Chicago phone book). Dresden has one foot in each world, the everyday existence we all live in, and the realm of the supernatural.

A word of warning for younger fans of wizardry, or their parents: this show is not aimed at children. The first episode, for example, includes some corpses who have been skinned and a boy stolen from his bed by the Raven Clan, creepy thugs-for-hire in the magical world. (My 10-year-old won’t be watching.)

In a phone interview, executive producer David Simkins said Dresden will solve a stand-alone mystery each week, while at the same time the writers thread a backstory for Dresden through the show that will slowly deliver clues as to who he is and how he got that way.

“The show is not just about magic and mayhem, but also about characters trying to find their place in the world,” Simkins said.

Dresden has a friendship with Lt. Connie Murphy (Valerie Cruz) of the Chicago Police, who is not aware of Dresden’s powers. Nevertheless, she’ll occasionally bring particularly baffling crimes his way.

Simkins sees Murphy, and her world, as the polar opposite of Harry Dresden’s supernatural realm.

“When you are with her, when you’re in the police station, we want to create a strong sense of reality,” he said. “When Dresden butts up against that world, it creates a collision, and the show exists in the middle of that collision.”

As Simkins acknowledges, the tricky part is finding the right tone for a show that wants to combine two genres — detective drama and otherworldly fantasy. Go in one direction and it’s too grim, go in another and it drowns in its own whimsy.

In the Dresden Files press kit, Blackthorne — a British actor best-known as evil mastermind Stephen Saunders on 24 — said he was attracted to the character for his non-heroic qualities.

“I very much appreciate how this guy was the reluctant hero, and how he was a regular guy who happens to be a wizard; therefore, he just happens to have to save the world because it’d be a waste to let those powers slip away and be of no use,” he said.

Although we see Dresden with a girl-friend, and there’s certainly romantic potential in his relationship with Lt. Murphy, Blackthorne said Dresden is far more afraid of relationships than he is of demons, ghouls, witches or werewolves.

Dresden shares his apartment in a seedy Chicago neighborhood — although The Dresden Files is filmed in Toronto — with Bob (Terrence Mann), a medieval wizard who was killed in 1057 for going too far into the dark arts. Bob’s ghost haunts Harry’s apartment, dispensing advice, warnings, and looking for a chance to regain his corporeal self.

In the early episodes, we learn a little of Dresden’s history, with more information to come as the season progresses. His mother died young, in yet-to-be-explained circumstances. His dad was a mediocre stage magician who didn’t possess any genuine magic powers. His uncle Justin did have power, though, and wanted to take young Harry from his dad.

Sometime between then and now, Harry killed his uncle, supposedly in self-defense.

Another word of warning: this is the kind of show where the dead might not be really dead, or stay dead.

The realm of magic is governed by the High Council, which Simkins described as a body of border guards between their world and ours. The Council’s agents are known as Wardens, and Harry’s Warden is Morgan, played by Conrad Coates. Even though the Council ruled that Dresden killed his uncle in self-defense, Morgan suspects otherwise, and keeps a very close eye on Dresden.

Simkins said The Dresden Files writers have taken care not to give Dresden too much power — otherwise, the show wouldn’t have much suspense.

“He pays a physical and emotional cost when he uses his magic,” Simkins said. “He’s not a bottomless pit of magical activity. He’s fallible and emotional and he can be hurt.”