See Maura Tierney's Law & Order debut on new season featuring Mariska Hargitay: 'I get to call her Liv'

It's been 33 years since Maura Tierney landed one of her first major acting gigs in a one-episode stint on Law & Order back in 1991. Although the E.R. alum says that, as she prepares to re-join the show for season 24 in a series regular role, she didn't recognize any familiar faces among the iconic crime procedural's ever-evolving cast or crew, one thing has remained the same over the last three decades.

“Dude, the crime is murder,” Tierney tells Entertainment Weekly when asked what kinds of cases her character, Lieutenant Jessica Grady, confronts this season after joining Detective Vincent Riley (Reid Scott), Detective Jalen Shaw (Mehcad Brooks), and District Attorney Nicholas Baxter (Tony Goldwyn). “But, there are extenuating circumstances around the murder!"

Like, for example, murder with a socio-technological message relevant to contemporary times, Tierney adds. Take episode 2, for which franchise icon Mariska Hargitay makes a temporary jump from SVU to the main series to assist Grady with a particularly oddball death.

"We're exploring an A.I. dating app, where the app goes beyond hooking you up with someone else, and basically it’s about creating an A.I. partner or boyfriend. That technology is here. People do have A.I. friends," teases Tierney. "That episode studies the complexities of when A.I. becomes a little too intimate."

Although she admits she was "fairly nervous" to board a show with such a historic pop culture imprint, Tierney didn't have trouble forming a connection with the Law & Order legacy and its cast. Tierney says she immediately clicked with Scott and Brooks over their mutual sense of humor, and calls her time with Hargitay "a blast" on set.

"It was funny to me because I read the script and I was like, 'Oh, I get to call her Liv,' which was very exciting and funny," Tierney says, referencing Hargitay's Capt. Olivia Benson. While she enjoyed working with Hargitay herself, she promises that there's tension brewing between their characters, which was equally as fun to dive into. "We don’t really get along, our characters. They get into a disagreement about how a certain legal matter should be handled, so it was fun to get into it with her a little bit," she adds, noting that Grady and Benson are definitely "not besties" — at least on episode 2.

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And, on the surface, that's just who Grady is. "She’s tough, and she’s very, very, very smart," Tierney stresses. "Her gut instinct is very strong, she leans on it, and she expects people to listen to her when she talks."

She's careful not to label Grady with more negative adjectives, though, because she senses that Law & Order will attempt to go beyond skin deep with its new addition and get to the root of "how her home life affects her at work" and in the field.

"They’re trying to adjust the show a little bit this season, and make it a little bit more active. They’re getting a little bit more personal with the characters," Tierney observes, but she's not quite ready to reveal all of Grady's secrets; she'll let the show do that for her.

"I certainly think she’s much less charming than anyone I’ve played. But, I don’t see that as a problem. The character has a hyper attention to detail, which serves her well in her job, but that doesn’t make her super fun," she says. "We’re going to have a sense of humor about her, but she’s a very strict boss and doesn’t care very much if the detectives under her like her or not."

Tierney, clearly amused, laughs a bit as she thinks of her career leading up to Law & Order, and the significance Grady holds for her: "I don’t think I’ve played a character like that before," she says. After all, the opportunity to play someone like Grady might only come around once every three decades.

Law & Order premieres Oct. 3 at 8 p.m. ET/PT, on NBC, with next-day streaming availability on Peacock. See EW's exclusive first-look photos at Tierney above.