The second time it happens, it's not Dean who notices, and he could kick himself. They're talking to the Millers' former neighbor, getting the backstory on Max's horrific childhood, when the man they're interviewing pauses and asks Sam if he's okay. Dean's focus evaporates in an instant, his eyes shooting to his brother. And sure enough, Sam's pinching the bridge of his noise, gritting his teeth. He still tries to play it off, because he's a Winchester, but Dean suddenly couldn't care less about this interview. Trying to avoid a scene for Sammy's sake, he wraps an arm around his brother and guides him to the Impala. Sam is still mostly steady on his feet – for the moment – but accepts Dean's help anyways. Dean, still flashing back to images of Sam on his knees, unresponsive, is beyond grateful.
Dean almost manages to get Sam in the car before the vision hits and Sam freezes. "Dammit, Sam," Dean whispers, anxiety starting to rise in his gut. He's already got the Impala's door open, and while Sam initially went rigid, he's starting to go limp. Dean takes as much of his brother's weight as he can in this position and gently guides him into the front seat. He kneels in front of the door, blocking Sam from view as much as possible. Sam's face is screwed up in pain, and Dean's heart aches with it. He puts a hand on Sam's knee, rubbing his thumb back and forth in what he hopes is a soothing gesture. The utter helplessness of it all is absolutely gutting Dean to his core. Even after the first time this happened, Dean had held onto the unlikely hope that it was a one-off freak occurrence. But the Winchesters could never be so lucky.
And Dean knows that he has to be strong for Sam, but damn it if this isn't scaring him shitless. He hates not knowing what's happening to his brother, and if things keep escalating at this rate… No, he can't think about it now. Sam's still gasping in pain, seeing whatever unspeakable horrors are coming next flashing before his eyes. Dean faintly wonders if he should be timing this, like you woulda seizure, but there isn't exactly a rulebook on how to deal with your brother's freaky psychic shit. All he can do is whisper comforting words, try to shield Sam from prying eyes, and watch his brother's breathing, and it's torture. The world moves around him – birds chirping, neighbors chatting, cars passing by – and Dean wants to scream at it all to stop so he can focus on Sam.
It's minutes later when Sam comes to, snapping back into awareness wide-eyed and gasping. "Sammy? You with me?" Dean asks, cautious.
Then Sam is rushing to explain the latest vision, trying to get Dean to start driving now, and Dean knows he won't be able to get Sam to give himself a minute. At least he's sitting this time, safe in the Impala. Dean acquiesces, standing up slowly and giving his brother's hair what he hopes passes for an affectionate ruffle and not the means of grounding himself – or, he hopes, the both of them – that it is. Sam locks eyes with him, seeing through the gesture. Of course he does, because the kid could read Dean like a book even before the psychic shit.
Sam's eyes soften, and he takes a few exaggerated breaths for Dean's sake. "I'm okay, Dean."
"Yeah, yeah," Dean dismisses him. He knows that Sam would say the same thing no matter what - he learned from the best. But Sam doesn't seem to be in immediate danger, so he slides behind the wheel and the boys take off.