He'd been here before, hadn't he? A hundred times, a hundred ways, Sam had felt Dean die in his arms. This time there'd be no Heat of The Moment to snap him awake, no Lilith to hunt down and kill, no Bobby to try and coax him into doing the right thing.
It was just Sam holding Dean, cold and still and dead.
When Cas didn't answer, when Metatron didn't reappear, when Sam could draw breath again, he carried Dean out of the building, over his shoulder, through the crowd of people waiting for Metatron to be their savior, to the Impala.
He opened the backdoor and gently laid Dean on the backseat. Sam knew he should get on the road, drive hell for leather to the Bunker, read every book and file and sheet of paper until he found something, anything to help Dean.
But he couldn't move. He couldn't do anything but stand there and stare at Dean's bloody face and broken body and will him back to life. But all that happened was Dean's skin grew more pale and the blood grew more dark against it.
Sam got a bottle of water from the trunk and washed Dean's face and hands, and then he drove them home.