Anthony LaPaglia and Roselyn Sanchez, wearing heavy-looking suits, latex gloves and somber expressions, are conversing at a Brooklyn gas station, about a block east of the famed River Cafe. He also carefully inspects a battered-looking beige van, abandoned there by a man who has kidnapped a 5-year-old boy.

On this July afternoon, when “Without a Trace” is in town to shoot exterior scenes for its fifth season, it’s 99 degrees in the shade – not that you can even find much of that on this tree-free concrete corner.

During breaks, Sanchez takes refuge in an air-conditioned SUV that’s parked and idling nearby. Crew members spritz themselves with water, and a wardrobe person runs out to blow-dry the back of a guest actor’s soaked shirt.

But LaPaglia, once a pro soccer player in his native Australia, doesn’t seem to break a sweat.

“I don’t heat up much,” LaPaglia later explains to a curious (and overheated) visitor.

The ability to stay cool when things get hot may come in handy for him this fall. After a long, successful run at 10 p.m. Thursday, LaPaglia’s hit CBS series made a bold move this week to 10 p.m. Sunday.

Though LaPaglia admits he was “a little surprised” when he first heard about the schedule change, he has faith in the wisdom of CBS President Leslie Moonves. He’s also heartened that summer repeats in the new time slot did well.

“As long as people know that we’re moving to Sunday night, I’m fine with it,” LaPaglia says. “In some ways, it weirdly takes the pressure off, ’cause Thursday night is such a battlefield about advertising dollars. I don’t really feel that now, so in the end, it may be the best thing that could have happened to the show. I think it could give us a bit more freedom creatively.”

Greg Walker, one of the show’s executive producers, especially likes that “Without a Trace” will follow two other Jerry Bruckheimer shows – “The Amazing Race” and “Cold Case.”

“What is CBS saying, “Race’ to “Case’ to “Trace’? It’s the all-Bruckheimer night, and we’re happy to be part of it,” Walker says. “Thursday night was great to us. We were blessed with an incredible lead-in, “CSI.’ And we got to compete against one of television’s all-time greatest shows, “ER.’ This is a different world for us.

“But it’s Season 5, and I think our challenges, whether our show was going to be on Thursday night or on Sunday night, remain the same. How do you keep it fresh and keep it interesting? Our attitude is, we’re going to bend it but not break it.”

On this New York City trip – one of two (summer and spring) that Los Angelesbased “Trace” makes each season to the city where the series is set – the crew is shooting outdoor sequences for several episodes. This one at the gas station was part of this week’s season opener, which has the team searching for that missing 5-year-old and his abductor after being tipped off by the kidnapper’s 12-year-old son.

The professional pairing of LaPaglia’s Jack Malone and Sanchez’s agent Elena Delgado is something viewers will see more of. “It’s an interesting dynamic,” Walker says, watching their scene. “It’s interesting to get this really new fresh rookie and then the seasoned detective.”

“Trace” fans also can look forward to another workplace romance, this time between Delgado and agent Danny Taylor (Enrique Murciano), whose past connection will also be made clearer.

The next episode, Walker says, “puts them in an undercover situation together where they have to address feelings that maybe wouldn’t have come out normally in the workplace, but the undercover situation brings them out,” Walker says, adding that Delgado, who has a daughter, will have custody conflicts with her ex. “Danny’s going to get in the middle of that, and that will complicate the new romance that they have.”

He pauses. “As we’ve seen before, it’s not exactly a recipe for success if you have a romance inside the office of “Without a Trace.’ Maybe they can break the pattern.”

Delgado’s undercover assignment, by the way, is a real attention-getter: To find a missing stripper, she’ll work as a dancer at the club where the woman was last seen. (Danny poses as one of her customers.)

Sanchez recalls how producers proposed the scenario to her during the show’s hiatus.

“They call one day saying, “Do you have a problem if you play an exotic dancer? I said, “No, I don’t. What do I have to do? What do you want me to say? I don’t have a problem. Get me out of this suit,”‘ she says. “I’m super-excited, because I was begging them to give me something like that.”

Though she loves “Trace” – and has become so friendly with co-star Poppy Montgomery that the two and their boyfriends vacationed together for two weeks in Mexico this summer – the procedural format can be confining for the regulars, Sanchez says.

“It’s never about the characters, per se; it’s more about the missing persons, so the guest stars get to do amazing work,” Sanchez says. “We’re just providing information. It becomes a little challenging. Sometimes we’re sitting there, me and Poppy, doing an interview scene with whatever guest star, and they do exquisite work, and we just go, “Oh, I wish I could be doing that.”‘

Meanwhile, Montgomery – whose Samantha Spade character has had failed office romances with Malone and agent Martin Fitzgerald (Eric Close) – will have “a big story involving a family mystery in her own life,” Walker says. “We’re going to explore why she became a missing-persons agent in the first place.”

“They came up with something that wasn’t romantically based, ’cause she’s run the romantic-love-triangle gamut, so to speak,” Montgomery quips on the phone about a week after this shoot.

She also hopes to have scenes this season with Mary Elizabeth Mastrantonio, who plays Anne Cassidy, the new woman in Malone’s life. “She’s so wonderful,” Montgomery says. “I would love to get the opportunity to be onscreen with her and explore that dynamic.”

LaPaglia, who did a play with Mastrantonio 15 years ago, says he was thrilled when she wound up on the producers’ short list of actresses to play Anne. “I loved her,” he said. “And I said, “I think she’s perfect.”‘ As I said to them, I don’t want to be with some 25-year-old. I want it to be age-appropriate, so that it looks like something that could really happen.”

In the season finale, the widowed Anne (who never had children), broke the news to the divorced Malone (father of two daughters) that she’s pregnant. He initially reacted badly. “There’s a whole “What are we going to do,’ because I’ve already been there, and she doesn’t really want to go there,” says LaPaglia. “It brings up a lot of interesting possibilities. I’m not sure where that’s gonna go.”

Says Walker: “We have two fantastic actors in Anthony and Mary Elizabeth. We really want to see them struggle with what I think is a real-life issue for people in their 40s. You’ve both had relationships that have ended in failure, ultimately, so you’re trying to figure out how not to make the same mistakes again while you still have time.”