Here’s the official synopsis for episode 21 of Supernatural titled ‘When the Levee Breaks’ which airs Thursday, 7th May. Do not continue reading if you don’t want to see spoilers!
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. Robert Singer directed the episode written by Sera Gamble