Time jump to after the season 7 finale.

Right after Cas leaves Dean in Purgatory.
Hell.
Meg was hanging on a rack, cuts running over her entire body. A demon, assigned by Crowley, was curving and cutting in her naked skin. Her screams echoed in the entire Hell, while Crowley was watching.
“Mr. Crowley!”
Crowley groaned and rolled his eyes. “What?” he said short while turning around.
“I found an intruder” a demon said. He was holding Cas’ collar and dragging him along. Cas looked up and saw Meg hanging, but he didn’t pay much attention to it.
“Well, what do we have here?” Crowley said soft.
“I want to make a deal” Cas said.
Crowley looked at Cas for a few seconds. Then he signed at the demon to leave. “A deal, huh? What did you have in mind?”
“I want you to keep me here. You can do whatever you want with me” Cas started.
“In exchange for what?” Crowley asked.
“You let Dean out of Purgatory” Cas said.
“I don’t know about that” Crowley said. “That Winchester has been a pain in my ass ever since I met him. Some time in Purgatory might do him some good”
“You don’t want him. You want me. I betrayed you and you’ve been waiting for a chance to punish me. Well, here’s your chance. Take it or leave it” Cas said.
Crowley thought about it for a few minutes. “What about your sweetheart up there?” he pointed with his thumb at Meg. Cas looked at Meg for a few seconds. “I don’t care about her”
A big smile appeared on Crowley’s face and he grabbed Cas’ hand and shook it. Then he whistled. The demon who was torturing Meg came down.
“Hang this one next to her” he ordered.
The demon grabbed Cas’ arm and jumped up.