Peter MacNicol Peter MacNicol

The world of CSI: Cyber is being filled out. 

Ally McBeal alum Peter MacNicol has joined the cast of CSI: Cyber as a new series regular, has learned.

The new drama stars Patricia Arquette as Avery Ryan, Special Agent in Charge at the Cyber Crime Division of the FBI in Quantico, Va., who is tasked with solving high-octane crimes that start in the mind, live online, and play out into the real world.

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MacNicol, whose credits also include 24 and Grey's Anatomy, will play Assistant Director Stavros Sifter, 40, a career FBI insider and Avery's supervisor. Sifter quickly rose up the ranks and positioned himself in a job where he is the clearing house between FBI Cyber and all other branches of government.  He is a shrewd and savvy networker as well as a charmer with a hint of malice.  

Jerry Bruckheimer and Jonathan Littman will executive-produce the drama, written by fellow executive producers Carol Mendelsohn, Anthony Zuiker and Ann Donahue.

CSI: Cyber will air Sundays at 10/9c starting midseason.

(Full disclosure: is owned by CBS.)