Here's the official episode guide for Nikita episode 21, "Betrayals":
RICH SOMMER (MAD MEN) GUEST STARS
- After Michael learns that Percy has ordered Divison to kill anyone who could decrypt the black boxes, he sends Nikita in to save the last person on the list, a CIA cryptographer named Malcolm (guest star Rich Sommer).
- Nikita kidnaps Malcom and takes him to Ryan (guest star Noah Bean) for protection.
- Meanwhile, Percy turns on Alex.