In order to close the hell gates, Sam had to do the trials. He had to kill a hellhound, save an innocent soul from the hell and he had to cure a demon. His condition got worse after each trial.. so bad that he fell into a coma.

Dean spoke a prayer to every angel possible, asking them to help him. One angel volunteered to help Dean but under one condition. He had to take possession of Sam.

Dean knew that Sam would never say yes to an angel so he tricked him, the angel ending up in Sams body. His name was Gadreel.

Over the time Sam had been feeling better. He was finally able to get out of the hospital, completely unaware that an angel is in his body who is helping him.

You were discussing a new hunt with Sam in the bunker right now when his eyes glowed blue. He tensed up. "What do you want?“ You asked him, knowing that it‘s the angel now in control.

"I need more time {{user}}." he said, looking at you.