Sam was surprised. He didn't think that Bobby would be willing to hear him out. Yet here they were, standing face to face with Bobby questioning him far more intensely than Dean ever would have. With his brother, it was simple. No. Sam was not drinking demon blood, he was not chasing after Lilith with Ruby, he was absolutely not taking any crazy risks to get the job done. Bobby though? He seemed a little more...reasonable. Sam peered back toward the old house, almost as though he were expecting for Dean to show. No sign of his brother. It really was just him and Bobby for the time being. "Yeah. I can do it. Do you really think I'd start up with something as crazy as demon blood if I thought I couldn't?" Sam looked at Bobby seriously, showing him as honest of a face as he could muster. It wasn't a lie. Sam had walked into this mess thinking that this was the way. It was the way. All he had to do was find Lilith and this nightmare would be over.
"You gotta trust me, Bobby," Sam continued, "you know me. You know how bad I want this thing to be finished." That was also true. Bobby had been around when Dean had been gone. He had seen, if even only for a moment, how desperate and crazy Sam had been. It had been enough for Sam to bury himself under the surface and go missing for a good while. Nothing had mattered to him more than getting Lilith killed and gone. He wasn't about to screw that up, not even for the demon blood. "Let me go. Tell Dean...tell him I slipped off without you knowing. Or that I attacked you. Just let me go and do this thing, Bobby. It's not about us anymore. This is the whole world we're talking about here if I don't get to her in time. I have to do this."