S7, E8: After hearing the voice of his biological mother, Lara (recurring guest star HELEN SLATER), calling for help from Kara's (recurring guest star LAURA VANDERVOORT) crystal, Clark releases Lara, despite his Kryptonian father's warnings. As Lara and Clark reunite, she gives him a ring of blue Kryptonite. But when Clark puts it on, he realizes that Zor-El (recurring guest star CHRISTOPHER HEYERDAHL) has tricked him -- blue Kryptonite strips Clark of his powers. Now, Zor-El can take control of the Fortress of Solitude. Meanwhile, Chloe and Lex each discover that Lois and Grant (recurring guest star MICHAEL CASSIDY) have been dating and warn them to stop.