Smallville Episode Details!

Episode 8x21 "Injustice":

DC COMICS CHARACTER PLASTIQUE RETURNS WITH FRIENDS

Chloe (Allison Mack) returns and begs Clark (Tom Welling) to kill Davis (Sam Witwer), claiming he can no longer keep the beast under control. Tess (Cassidy Freeman) has assembled a team of meteor freaks, including Plastique (guest star Jessica Parker Kennedy), to track down Davis so Clark can kill him. However, things get out of hand once Tess’ team discovers she is double-crossing them. Aaron Ashmore and Justin Hartley also star. Tom Welling directed the episode written by Al Septien & Turi Meyer.

Source: CW