Dexter fans can rejoice because the serial killer that they love so much (perhaps that's something to unpack at a later date) is back on our screens, albeit in a much younger form. Dexter: Original Sin has started its first season and it's getting into all the dirty deets on how Dexter started his serial killer vigilantism. The series has plenty of familiar characters from the original series (with new, younger actors taking on the roles) and some brand-new characters too. So, let's get into who's on the cast and what roles they're taking on.

Patrick Gibson as Dexter Morgan

Dexter Morgan is fresh out of college and starting his career at the Miami Metro Police Department's forensics unit...and as a serial killer. Cutting into cadavers at school and going out on hunting trips isn't doing much to satisfy his murderous cravings and, as the title of the show implies, we'll be getting a more detailed look into how Dexter's first kill(s) came to be.

Patrick Gibson is an Irish actor who you may recognize from the Netflix sci-fi series The OA and Shadow and Bone. He also starred alongside Nicholas Hoult in the 2019 biopic Tolkien.

Instagram: @paddygibson

Christian Slater as Harry Morgan

Dexter's dad, Harry Morgan, may be dead in the original series, but in Original Sin he's well and alive (at least for now). He's a well-respected detective at Miami Metro and he's very aware of his son's murderous tendencies. He's even trying to keep Dexter from giving in to them. But taking Dexter hunting so that he can kill animals just isn't scratching that itch, so he ultimately supports his son's vigilantism.

Christian Slater has a loooong resume, so there's a good chance you'll recognize him. He's starred in TV shows like Dr. Death, Mr. Robot and Dirty John, and movies like Heathers, Unfrosted and Blink Twice.

Instagram: @realchristianslater

Patrick Dempsey as Captain Aaron Spencer

There's not a lot that's McDreamy about Captain Aaron Spencer—with his slicked-back hair and full mustache, he's looking verrry early '90s. He's the hard-ass captain of Miami Metro's homicide department and has a long relationship with Harry Morgan.

Patrick Dempsey is obviously best known for playing Dr. Derek Shepherd on Grey's Anatomy or Robert in Enchanted and Disenchanted, but in Original Sin he's getting to take on a bit of a grittier role and we can't wait to see it.

Instagram: @patrickdempsey

Christina Milian as Detective Maria LaGuerta

Detective Maria LaGuerta is another character who's coming back from the original Dexter series, but in a younger form. In the original show she's already captain of the homicide department, but in Original Sin, she's still a detective who hasn't worked her way up the ranks yet.

Singer-songwriter-actress Christina Milian is taking on the role, and you may be familiar with her from the Netflix Christmas movie Meet Me Next Christmas or, my personal favorite, singing the Kim Possible theme song "Call Me, Beep Me."

Instagram: @christinamilian

Sarah Michelle Gellar as Tanya Martin

Tanya Martin is a new character to the Dexter franchise. She's Dexter's first boss at Miami Metro and is the CSI chief—the job Dexter eventually takes over. Sarah Michelle Gellar is listed as a special guest star so, if I had to put my money on it, I'd say there's a good chance Tanya won't be around for too long.

Sarah Michelle Gellar needs no introduction, but if you happen to have lived under a rock for the past decade or three, she's best known for starring in Buffy the Vampire Slayer, Scooby-Doo and Cruel Intentions (the movie, not the new TV show).

Instagram: @sarahmgellar

James Martinez as Detective Angel Batista

In the original series, we see Angel Batista make his way up to becoming a lieutenant but in Original Sin, he's back to being a detective. He's always been an honest and kind addition to the police department, adding a much more human touch to his crime scene investigations than Dexter ever did.

James Martinez has already been in a few beloved shows including Billions, The Deuce, House of Cards and Love Victor and he's got plans to star in an upcoming crime series with Jessica Chastain called The Savant, which BTW was inspired by this Cosmopolitan article from 2019!

Instagram: @urjamesmartinez

Molly Brown as Debra Morgan

We know in the original series that Debra is part of Miami Metro's homicide team, but in Original Sin, she's just Dexter's younger, school-aged sister. She's got some resentment toward her (very strange) brother and feels like he's holding her back from getting to be a regular teenager, and it doesn't help that her dad is forcing her to try to help Dexter socialize.

Molly Brown is a relatively newer actress on the scene, making her TV debut in 2018. Since then she's been in shows like The Marvelous Mrs. Maisel, Billions and Law & Order: Special Victims Unit

Instagram: @mollyelizabethbrown

Reno Wilson as Detective Bobby Watt

Detective Boby Watt is Harry Morgan's best friend and partner at Miami Metro. He's even Debra's godfather, so that gives you an idea of just how close he and Harry are. But, interestingly, he was never in the original series even though he's suppossed to have known Dexter his whole life and be really close to the family.

Bobby will be played by Reno Wilson, who you might recognize from shows like Fatal Attraction, Bel-Air, Good Girls, and Mike & Molly.

Instagram: @renowilson1

Alex Shimizu as Vince Masuka

Vince Masuka is another familiar name played by a fresh new face. He works on the forensics teams alongside Dexter and he's probably best known for cracking some, er, iffy jokes. He also has it bad for Debra so maybe we'll eventually see how that all started.

Alex Shimizu is probably best known for playing Tadashi in The Blacklist or Toshiro Furuya in season 2 of The Terror, but Dexter: Original Sin may just be his biggest project to date.

Instagram: @alex__shimizu

Michael C. Hall as Dexter Morgan's internal monologue

Yup, that's right, the original Dexter is making an appearance (well, figuratively speaking) in Dexter: Original Sin as Dexter Morgan's internal monologue voiceover. Fans of the OG show will love that familiar touch, I'm sure.

Michael C. Hall is obviously best known for playing Dexter (he started playing it in 2006, after all) but he's also appeared in The Crown as President Kennedy, the Netflix series The Safe and Six Feet Under as David Fisher.