The producers were impressed by his performance and when, in the second season, he auditioned for the role of turncoat FBI agent Alex Krycek, he was successful.

[6] In the season three episode "Apocrypha," Krycek was left to die in an abandoned missile silo with an alien ship.

Lea continued to play Krycek, who became a nemesis not just of Mulder and Scully but particularly of A.D. Skinner (Mitch Pileggi).

Lea co-starred with Lau Ching-Wan, Theresa Lee and Bif Naked in the Hong Kong-Canadian film Lunch with Charles in 2001.

Nicholas has also guest starred in the ABC remake of the sci-fi series V. He is also a member of the board of directors for the Lyric School of Acting in Vancouver.