An old case is coming back to haunt Olivia Benson (Mariska Hargitay) in the 300th episode of "Law & Order: SVU." How old? It's from the show's first episode thirteen years ago.

"SVU" is celebrating the milestone by remembering the past. The episode will be focused on original players Hargitay, Richard Belzer and Dann Florek.

“I thought, if we’re doing a 300th episode, it’d be nice to have some callbacks to the first episode. So we tried to do that a couple of different ways,” Leight told TVLine.

The episode will also feature many actors who appeared in the series' first episode, but they'll be playing different roles. Here's how NBC describes the episode:

IN THE SERIES' 300TH EPISODE, A CHILD ABDUCTION INVESTIGATION RE-OPENS THE THIRTEEN YEAR-OLD COLD CASE OF ANOTHER MISSING BOY In the series' landmark 300th episode, a young boy from Morningside Heights is kidnapped while in the care of his father, and the investigation reminds Captain Cragen (Dann Florek,) Sergeant Munch (Richard Belzer) and Detective Benson (Mariska Hargitay) of an unsolved kidnapping that occurred in the same neighborhood thirteen years ago. While the entire squad races against the clock to find the missing boy, Benson vows to learn from past mistakes to set both cases right. Also starring Ice-T (Detective Odafin Tutuola), Danny Pino (Detective Nick Amaro) and Kelli Giddish (Detective Amanda Rollins.) Guest starring Tom Sizemore, Hamish Linklater, Mili Avital, Alex Karpovsky, Chris Orbach and Jenna Wolfe.

Take a look at the trailer below and click through the slideshow to see how the cast and crew celebrated the big episode, which airs Wednesday, October 24 at 9 p.m. ET on NBC.

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  • "Law & Order: SVU" Season 15

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  • "Vanity's Bonfire"

    Jessica Hecht as Gillian Webster

  • "Vanity's Bonfire"

    Ice-T as Det. Odafin "Fin" Tutuola, Kelli Giddish as Detective Amanda Rollins

  • "Vanity's Bonfire"

    Scott Bakula as Kent Webster

  • "Vanity's Bonfire"

    Scott Bakula as Kent Webster

  • "Vanity's Bonfire"

    Scott Bakula as Kent Webster

  • 300th Episode Celebration

    "SVU's" 300th episode cake.

  • 300th Episode Celebration

    Dick Wolf and the cast of "SVU."

  • 300th Episode Celebration

    Co-Executive Producer Michael Smith, Executive Producer Julie Martin, Co-Executive Producer Ed Zuckerman, Ice-T as Detective Odafin 'Fin' Tutuola, Danny Pino as Detective Nick Amaro, Kelli Giddish as Detective Amanda Rollins, Dann Florek as Captain Donald Cragen, Executive Producer Dick Wolf, Richard Belzer as Detective John Munch, Mariska Hargitay as Detective Olivia Benson, Executive Producer Peter Jankowski, Co-Executive Producer Arthur Forney, Executive Producer Warren Leight.

  • 300th Episode Celebration

    Ice-T as Detective Odafin 'Fin' Tutuola, Danny Pino as Detective Nick Amaro, Kelli Giddish as Detective Amanda Rollins, Dann Florek as Captain Donald Cragen, Executive Producer Dick Wolf, Richard Belzer as Detective John Munch, Mariska Hargitay as Detective Olivia Benson, Executive Producer Warren Leight.

  • 300th Episode Celebration

    Mike Canosa from transportation, Production Accountant Greg Cattano, Executive Producer Peter Jankowski, Eddie Coonan of transportation, Dann Florek as Captain Donald Cregan, Executive Producer Dick Wolf, Richard Belzer as Detective John Munch, Mariska Hargitay as Detective Olivia Benson, Co-Executive Producer Arthur Forney, Director Jean DeSegonzac, John Raffone of transportation, Publicist Pam Golum -- "Law & Order: Special Victims Unit" celebrates 300 episodes with the current cast and crew who worked on episode 1.

  • 300th Episode Celebration

    The cast of "Law & Order: SVU."

  • 300th Episode Celebration

    The cast and crew of "Law & Order: Special Victims Unit" surround Executive Producer Dick Wolf to celebrate the 300th episode of the show.

  • 300th Episode Celebration

    Dick Wolf.

  • 300th Episode Celebration

    Richard Belzer, Dick Wolf & Mariska Hargitay.

  • 300th Episode Celebration

    Mariska Hargitay as Detective Olivia Benson, Co-Executive Producer Arthur Forney, Co-Producer/Casting Director Jonathan Strauss, Executive Producer Warren Leight.

  • 300th Episode Celebration

    Dick Wolf and the cast celebrate "SVU's" 300th episode.

  • Law and Order: SVU Season 14

    Mariska Hargitay as Detective Olivia Benson.

  • Law and Order: SVU Season 14

    Jason Cerbone as CEA Counselor Terrence Quinn, Dann Florek as Captain Donald Cragen.

  • Law and Order: SVU Season 14

    Dean Winters as Detective Brian Cassidy, Danny Pino as Detective Nick Amaro.

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