Dean's been learning though. About himself, about how to fix it. "Our changing bodies," he joked to Cas, as Cas explained the wiring in his arm. "You need to know how to take care of yourself," Cas said, and Dean's never sure whether Cas really doesn't pick up on the humor or whether he's just ignoring it.

Dean knows how to hack into himself. He goes to Cas's lab at night and he cuts his wrist open, hooks up a blue wire tucked under his tendon into the main computer. His vision flickers when the download starts, and his skin tingles. His eyes start to water.

The first memory: Dean remembers pulling back his fist, and a terrified face, and then--