Sarah Michelle Gellar to play Dexter’s boss in prequel series

American actress Sarah Michelle Gellar will take on the role of the boss of serial killer Dexter Morgan in a new prequel series.

The Buffy The Vampire Slayer star, 47, will be playing Tanya Martin, the Crime Scene Investigation (CSI) chief at the Miami Metro Police Department opposite future blood spatter analyst Morgan, played by Irish actor Patrick Gibson.

Gellar wrote on Instagram: “It’s going to be a bloody good ride.”

Best known as Buffy Summers in the hit supernatural show, as well as 1990s movies Cruel Intentions and I Know What You Did Last Summer, Gellar has recently been in the supernatural teen series Wolf Pack and black comedy film Do Revenge.

Geller also shared an Instagram story, showing the first page of the script for the pilot, written by showrunner Clyde Phillips and directed by Heathers director Michael Lehmann.

Set 15 years before the original hit series, Dexter: Original Sin will chronicle the start of the career of the lead character, originally played by Michael C Hall in the hit show and sequel Dexter: New Blood.

It was already announced that Heathers and True Romance actor Christian Slater has been cast as Harry Morgan, a homicide detective and the adoptive father of Dexter who tries to channel his dark urges to fight crime.

Sex And The City actor James Remar had previously played the role in the Dexter show, which ran for eight seasons between 2006 and 2013.

BAFTA Awards 2009 – Press Room – London
Christian Slater will play Harry Morgan, the adoptive father of the titular character in Dexter: Original Sin (Ian West/PA)

Across 10 episodes, Dexter: Original Sin will be set in 1991 Miami.

It will see how Dexter learned to adapt The Code of Harry to help him find and kill people who he feels deserve to be eliminated from society without getting on law enforcement’s radar while beginning a forensics internship at the Miami Metro Police Department.

There have been reports of more franchise spin-offs in development including one focussed on Dexter’s son, Harrison Morgan, played by Jack Alcott in Dexter: New Blood, and the Trinity Killer.

The killer, a family man called Arthur Mitchell, who was originally thought to kill in threes and was portrayed by 3rd Rock From The Sun actor John Lithgow, appeared in the fourth season.

The franchise is based on the books by novelist Jeff Lindsay.