Stiles is freaked out enough to let Scott come up with all the plans, Scott is freaked out enough to blow it all to hell.

Stiles: "Deaton, the alpha? Your boss."
Scott: "No."
Stiles: "Yes, murdering psycho werewolf."
Scott: "That can't be."
Stiles: "Oh come on. He disappears, and that thing shows up ten seconds later to toss Derek 20 feet through the air? That's not convenient timing?"
Scott: "It's not him."
Stiles: "He killed Derek."
Scott: "No, Derek's not dead. He can't be dead."
Stiles: "Blood spurted out of his mouth, okay? That doesn't exactly qualify as a minor injury. He's dead, and we're next."
Scott: "Okay, just... What do we do?"
Stiles: "We get to my jeep, we get out of here, you seriously think about quitting your job, good?"

Stiles insists so much on Derek being dead as if he wishes this so that the whole mess with the werewolf can be over so that he doesn´t have to deal with Derek anymore. It's not that he doesn't care, but he certainly doesn't want to care.

Stiles: "Yeah, and Derek had to be shot with a wolfsbane-laced bullet to even slow him down, you remember that?"
Scott: "Then we...we have to... We have to find a way out and just run for it."
Stiles: "There's nothing near the school for at least a mile."
Scott: "What about Derek's car?"
Stiles: "That could work. We go outside, we get the keys off his body, and then we take his car."
Scott: "And him."
Stiles: "Fine. Whatever."

Stiles's reactions to Derek's alleged death are weird. The face Stiles makes when he mentions Derek's body. It's fear and disgust, but that boy was gleeful at finding Laura's body or thinking that Derek writhing in pain was awesome, that kid gets excited when there's a dead body. The fact that Stiles is having trouble with the thought of Derek dead so much isn't about the dead body so much as it is about Derek. Scott wants to take Derek´s body along and Stiles agrees reluctantly.

Scott: "It's Derek. It's Derek Hale."
Jackson: "Derek killed the janitor?"
Allison: "Are you sure?"
Scott: "I saw him."

Stiles' reaction to Scott accusing Derek is one of disbelief. Stiles cannot believe that Scott would do this after insisting that Derek was still alive. Stiles' face says What are you doing, Scott? You think this is fair? You think this is clever? Because if Derek is really truly dead, the lie would blow up as soon as the police would find Derek's body. But if Derek was still alive, this is just a terrible thing to do to anyone. Stiles may not trust Derek but he knows enough to know this is wrong. Scott is fucking it all up for no particular reason and Stiles is too freaked out to do anything other than follow his lead.

Stiles: "Okay, first off, throwing Derek under the bus, nicely done."
Scott: "I didn't know what to say. I had to say something. And if he's dead then it doesn't matter, right? Except if he's not. Oh, god, I totally just bit her head off."
Stiles: "And she'll totally get over it. Bigger issues at hand here, like how do we get out alive?"

Stiles is really offended for Derek being betrayed, not for Scott making his life harder with a bad choice. Scott defends himself at once. Stiles asserts Derek's death to make sure Scott doesn't try anything stupid.

Sheriff: "You sure it was Derek Hale?"
Scott: "Yes."
Stiles: "I saw him too."

Stiles has to say this to save his best friend from being a liar. Stiles will back up his bro until the end. Maybe one day Stiles won´t do this anymore when Derek somehow will become more important to Stiles than Scott.

Stiles wears the same clothes as in Heart Monitor.