Now here’s a love letter to “CSI” devotees: EW has learned exclusively that William Petersen will reprise his role as Gil Grissom with a cameo in an upcoming episode. The actor – who left the show in January 2009 – already shot his appearance on the CBS drama and we’re told his return involves Jorja Fox, who plays Gil’s on-screen wife Sara. It’s unclear exactly when he’ll appear back in or around the lab, but TV Line teased that it may occur this week.

As EW first reported in December, the writers paved the way for a possible Petersen return by penning an episode that introduces Gil’s long lost mother, played Phyllis Frelich. In the Feb. 3 show, a murder occurs at a school for the deaf where Grissom’s mom is a professor. Sara goes to investigate but ends up facing an unexpected challenge - a surprising lack of affection from her mother-in-law. Apparently, Grissom’s mom never felt that Sara was the one for her beloved Gil so the two women have a few fences to mend. The episode also stars Oscar winner Marlee Matlin as a school colleague who not only serves as Mrs. Grissom’s protege but used to date Gil. Guess who momma Grissom prefers?

Fans are supposed to think that Gil is constantly on the move so he and Sara maintain a long-distance relationship. This week’s story is a continuation of an arc that started way back in season one’s memorable “Sound of Silence” episode, in which we first learn that Gil can sign because he grew up with a deaf mother.

When Petersen left, both he and his fellow producers promised that the longtime TV and stage actor would return occasionally. Back in 2009 when he was preparing for his departure, Petersen told EW exclusively that while he won’t miss playing Gil, he hopes fans won’t get too shaken up over his character’s absence. “I think there’s a way for the audience to remember him, like losing a great co-worker they’ve known for years,” Petersen said. “He didn’t die in a plane crash, he didn’t get a brain tumor. He’s out there.”