“Smallville” and “Supernatural” continue their build-up to their season finales tonight, with all new-episodes airing on the CW.

SMALLVILLE: (8:00-9:00 p.m. ET) — Episode: “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. Erica Durance, Aaron Ashmore and Justin Hartley also star. Mairzee Almas directed the episode written by Al Septian & Turi Meyer (#3T7471).

SUPERNATURAL: (9:00-10:00 p.m. ET) — “When the Levee Breaks”
DEAN AND BOBBY TRAP SAM IN THE PANIC ROOM — Dean (Jensen Ackles) and Bobby (Jim Beaver) lock Sam (Jared Padalecki) in Bobby’s panic room so he can detox from the demon blood. However, as Bobby sees more seals are being broken he tells Dean they should let Sam out to help them fight the impending apocalypse. Dean disagrees and goes to Castiel (Misha Collins) for help. Sam and Dean have a big blowout confrontation. Robert Singer directed the episode written by Sera Gamble (#3T7521).