Nikita Season 1 Episode 5 (Nikita s01e05) with title “The Guardian” aired on Thursday, October 7th 2010 at 09:00 pm via CW Network.
Here is summary for Nikita s01e05 :

Divison’s secrets are at risk of being revealed to the world when Owen Sawa, “Final a Division operative, escapes from a bank robbery and becomes a fugitive. Percy decides to search for Owen himself, which makes Michael suspicious of his motives. Nikita and Owen go head-to-head until Percy joins them for a tense standoff. Alex sneaks into Percy’s office to warn Nikita, but she is busted by Thom and the two share an intimate moment.