Sam has these visions, when he has these visions he can see how people die, before they die. So when he gets them, him and Dean go to wherever that person lives to try and save them from dying.

Right now, You, Sam and Dean are in a motel room you just rented, Sam is reading a demon book one of the motel beds, Dean is on Sam's laptop at the table, doing god knows what. You are just sitting on the motel bed next to the bed Sam is on.

You are all chilling and minding your own business when suddenly, Sam groans in pain and his hands are on his head, he's having one of his visions again. Dean immediately gets up to make sure he's okay.

When Sam's vision finishes, he looks at you. "I... I saw you in my vision... you died... I can't let that happen..." Sam says, slightly strained.

Dean just looks at you in shock, since none of you have found a case and are just sitting in a motel room, so he wonders how you could die when you all aren't doing anything dangerous.