NEW YORK — As she nears the end of her freshman season starring on the CBS drama “Unforgettable” and, more immediately, faces another long shooting day as the detective who never forgets a clue, Poppy Montgomery sips her morning latte and does a little remembering.

For instance, she thinks back on her former series, “Without a Trace,” and how hard it was when that series concluded three years ago. For seven seasons she played Samantha Spade, a field agent in a missing persons task force, “and when you’ve done one character that long,” she says, “there’s a grieving process, almost, when it ends.”

She had also had a baby, Jackson, with then-partner Adam Kaufman as the show drew to a close, so she opted to take time off from her career.

But after spending Jackson’s first years as a stay-at-home mom, Montgomery got the script for “Unforgettable.”

She was being invited to play Carrie Wells, an NYPD detective whose rare condition renders her incapable of forgetting anything, including crime-solving details that no one else would even notice, let alone remember.

Montgomery, like millions of others, had seen a “60 Minutes” story in fall 2010 that explored the real-life condition called highly superior autobiographical memory and featured actress Marilu Henner, one of just a handful in the world who have this gift of total recall. (Henner would become a consultant for “Unforgettable,” which airs Tuesday at 10 p.m.)

“That was a fascinating report,” Montgomery says, “and I was intrigued by the character I was being asked to play. I also liked that I would get to do stunts: I like playing tough, ‘cop-py,’ gunslinging chicks.

“And I got to have red hair! “I was a redhead when I first came to America,” she says, noting that as a child growing up in Australia, she had hair that was “red like Pippi Longstocking’s.”

At 19, she left Sydney for Hollywood, determined to make it as an actress. In 2001, she won the starring role in “Blonde,” going blond as Marilyn Monroe in the TV film of the Joyce Carol Oates novel.

“My hair stayed blond for ‘Trace, ’ ” she goes on. “Then, when ‘Trace’ was done, I didn’t let my natural hair color grow in ... but still I decided to go closer to what I believed at that point was my natural hair color. Now I feel like an honorary redhead. But it’s a tricky color to maintain.”

No “Unforgettable” viewer would find fault with the chromatic luster of her russet tresses. But hair isn’t Montgomery’s sole concern these days: She is the centerpiece of a weekly hour drama with plenty of action and lots of dialogue for her to learn.

It represents a major promotion from “Trace,” where she was one of the team led by series star Anthony LaPaglia.

Now she is a leader, with a supporting cast comprising Michael Gaston, Kevin Rankin, Daya Vaidya, Jane Curtin and Dylan Walsh. Was Montgomery prepared for the burdens of stardom?

“By now I know what I’m doing,” she sums up in her soft Aussie accent, which sounds indistinguishable from a velvety Southern twang and can turn the word “dance” into two syllables. Now 36, “I’m older — and wiser, I like to think. And on this show I’m realizing how much I didn’t know that I knew, from seven years of doing it over and over on ‘Trace’ and absorbing so much from the people I worked with.

“I’m also a mother, so I’m a little more grounded in my world,” she adds, pointing to one of her several discreetly placed tattoos: Her inside right wrist is inscribed “Jackson.”

Another one, on her left foot from her teens, says “Faith not Fear.”