When Diaz excuses himself, Coulson tells his team to cover the back door and then goes in pursuit, while back in the lab, Fitz and Simmons discuss the possibilities attendant to Simmons' new theory -- until Skye realizes that the satellite is picking up a new reading in the firehouse. Coulson catches up with Diaz, who confusedly asks if he hears a humming noise, and I guess I should point out that in the cold open, Cross didn't appear to feel ill the way Diaz does now, which seems like an inconsistency given that Diaz at this point looks like he wandered over from The Walking Dead. Coulson, looking more and more concerned, says he doesn't hear anything before asking if Diaz was in New York with the others -- and then a metal pan floats up into the air behind Diaz, prompting Coulson to draw his gun and tell him to stop it. Diaz doesn't understand, but May reports that she's found a Chitauri helmet, a picture of which she immediately sends to the science team. Simmons concludes that the thing caused a cranial discharge, while Diaz tells Coulson that the helmet is just a souvenir from the battle, and someone first touched it a couple nights ago, as it was rusty. Simmons urgently pipes up for May not to touch the thing before explaining that Diaz isn't using a weapon -- he's infected with an alien virus.
Diaz tells them he, Cross and Whalen were bored and decided to clean the thing, and then his brain catches up with his mouth as he realizes, like Whalen and Cross, he's a dead man. Coulson tells his team to clear everyone out and closes the door, whereupon Diaz despondently concludes that he's going to end up like the others. Coulson grimly asks him to sit and then essentially asks if there's anyone to whom he can pass on some last words; when Diaz just stares into space, Coulson tells him he's been where Diaz is, "so please believe me when I tell you, you don't have to be afraid." Well, it's a nice sentiment, Coulson, but forgive me if I dispute your authority given that you haven't actually had a double-strength lightning bolt explode out of your forehead. Diaz foggily wonders what he means, so Coulson tells him he got hurt once, "and… I died. Some say it was only for eight seconds, but I know it was more than that." I'll say! At least he doesn't mention how magical a place is Hawaii. In all seriousness, though, this is the best bit of work I've seen from Clark Gregg so far as he earnestly tells Diaz he knows he wasn't here -- he was there. Choosing to believe, Diaz asks what there is like, and Coulson smiles that it's beautiful, which even affects May, listening on the comm. However, a knife then floats into the air and Diaz looks at Coulson: "You'd better get going, buddy." Coulson doesn't want to -- it's fairly clear -- but he does, and once he's taken a place at May's side and she's looked at him with some concern, they see electric blue light flare up from within. I'm telling you, people may be enamored of Coulson's quippery, but what will make the character work for me is his heart. Or whatever took its place.