Rosanna Arquette will make a guest appearance on her little sister Patricia Arquette’s “Medium” series in an episode which airs Monday, April 7.

Rosanna Arquette will play a femme fatale in a murder case that Patricia’s mediumistic character Allison DuBois character is investigating.

“This episode is about this black-widow woman who's seducing men and killing them,” Patricia revealed to TVGuide.com. “It's fun because our killers aren't usually women.”

Patricia, who has been starring as the soft-spoken mother of three who has psychic abilities and thus works as a research medium for the Phoenix, Arizona, district attorney's office since early 2005, has apparently been trying for that long to convince her older sister to join her on “Medium.”

In Monday’s episode, Allison DuBois and Det. Lee Scanlon (David Cubitt) will strive to track down the femme fatale after two young men are brutally murdered.

The role apparently suited Rosanna, who says: “When [executive producer] Glenn Caron called, I was like, ‘Ooh, I'd like to be a killer! A lady killer.’”

Caron was similarly enthused to have her on the set. “One of the nice things about being in business with Patricia Arquette is you get access to all of these other Arquettes,” he joked, referring to his collaboration with brothers David and Richmond. “I can buy them, trade them, absolutely. It's like having your own little repertory!”

The first directed, the second acted in “Medium” episodes.

Patricia Arquette received the Emmy in the Outstanding Lead Actress in a Drama Series category in 2005 and was nominated two more times. She ahs also received Golden Globe and SAG nominations for this role.

The cast also includes Jake Weber as her ever-supportive husband, and Miguel Sandoval as D.A. Devalos. Both have been nominated for prestigious television awards.