S04E21: 'When The Levees Break'

After Dean witnesses his dependence on demon blood, Sam finds himself barricaded into Bobby’s panic room in a last-ditch attempt to kick his habit.

Battling from severe withdrawal and suffering hallucinations, his condition leads Bobby to confide in Dean about his chances of recovery.

Matters are further complicated when a spate of murders signals that Lillith is breaking more seals, leading Bobby and Dean to clash over Sam’s role in proceedings.

Nevertheless, Bobby’s dire prediction leads Dean to seek Castiel’s help, resulting in an unexpected deal being struck much to the confusion of Anna. Elsewhere, Ruby returns with a possible link to Lillith and unwelcome news about the final seal.

As Sam’s condition deteriorates, Dean makes a shocking admission about his brother’s future and tensions reach boiling point when the Winchesters are forced to face each other in a violent showdown where some painful homes truths are eventually revealed.