Episode: 7×08 (Season 7 Episode 08)
Name: Blue
Originally Aired: Nov. 15, 2007

Plot: Clark hears the voice of his biological mother, Lara, calling for help from Kara’s crystal and decides to release her, despite Jor-El’s warnings. Lara and Clark reunite and she gives him Jor-El’s ring, which contains blue kryptonite. As Clark puts it on, he realizes Zor-El manipulated the whole thing and that blue kryptonite strips him of his powers, enabling Zor-El to take control of the Fortress of Solitude. Meanwhile, Chloe and Lex each discover Lois and Grant have been seeing each other and warn them to stop.Source: The CW