Supernatural (4.21): When the Levee Breaks

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.

Air Date: Thursday, May 07, 2009

Dean and Bobby lock Sam 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 for help. Sam and Dean have a big blowout confrontation. Source: The CW

04/17 - The boys will hear from Rufus in Episode 21, which is titled "When the Levee Breaks" and airs May 7. Source: TV Guide Online