Pavel hasn't kept a precise list of the horrible things he wants to never do, but helping Chief Engineer Scott load his captain into a radiation-absorbent casualty liner was definitely near the top.
He flees sickbay for engineering as quickly as he can without drawing attention. On the way he formulates the convenient fiction that it's because the ship is barely functional, and thankfully never has to put it to use. (He soon recognizes that he's not the only member of the Enterprise's crew functioning on an autopilot mode grounded in emotional shock, yet that brings him no comfort.)
There's plenty to do, and Pavel throws himself into it. The adrenaline of his own imminent death is slow to wear off; as it does, he feels like a towel that's been wrung too tight. He makes a good dent in the work that's facing engineering, though; hands off a few things, clears up others, and identifies possible solutions for outstanding ones.
Just as he's thinking he might have earned some rest, Mr. Scott finds him and tells him the impossible story of the captain's return to the world of the living. He's too ragged to feel the relief he knows is there, but he makes an effort, and it's enough for Mr. Scott (who also isn't effusive, and later Pavel will wonder about that). They go over the status of engineering and what remains to be done and what order to do it in. When Pavel slips into Russian for the third time without realizing it, the Chief orders him to go to sleep, and of all the orders anyone has ever given Pavel it's one of the easiest to follow.
It takes them nearly a week to get the Enterprise docked to Starfleet 6, at which point Mr. Scott stops putting off the unavoidable task of powering down the warp core so they can replace it. (Starfleet wants the Enterprise back up and running as fast as possible, and repairs would take much longer that a full replacement. The Chief uses it as an excuse to get an upgrade for the ship.) Pavel's noticed the Chief doesn't relish the idea of being around the old core, so he offers to be on the team.
The first session is the worst, because there's still tiny spots of blood in the outer chamber, on the glass and the wall. Pavel cleans it up the second he notices it; out of the corner of his eye, he sees a stricken look flicker over the Chief's face before he clears his throat and starts issuing orders. Pavel is proud that his hands don't shake the whole time they're at work.
He hears a variety of stories from other engineers: the Vengeance destroying a large portion of San Francisco, the Commander chasing Khan down in the resulting ruins, the captain's successful return to life. He keeps his mind on the work, though, since what lurks outside the focus needed to repair the ship isn't something he's ready to face.
A week later, he finds himself working with Mr. Scott on the final plans for installing the new core when the Chief Engineer says, out of the blue, "You know none of it's your fault, or anything, right?"
Pavel freezes, and feels his breath come short. He tells himself it's fine, everything's going to be fine, then can't stop himself from blurting out, "I--can't help but think, sir, that if I'd just been able to--"
"No, son, just--look." The Chief steers him to a seat on the steps leading to the warp core and drops into place beside him. (Pavel sees, at this proximity, that Mr. Scott is battling much more than mere physical exhaustion.) "There's only room to blame three people for everything that happened, and those seats are currently occupied by Admiral Marcus, Khan, and the captain himself. You'll have to unpack your bags for this guilt trip. The shuttle's full up."
Pavel swallows and looks down at the floor, toying with his communicator. "Maybe if--"
"No. No maybes, not buts, no ifs. What got the captain killed was horrible people doing horrible things and some incredibly pig-headed decisions." Mr. Scott looks away, his expression bleak. "Not all of them the captain's, when you get down to it."
Pavel feels confusion replace some of his self-doubt. "Sir?"
"I mean, me, *my* decision to quit. I could've--I could've stayed on the ship and figured something out. I don't know, maybe engaged in some creative excuse-making and mutiny to get the torpedos off-loaded when the captain wasn't looking." The Chief shakes his head and runs a hand through his hair. "I put you in a horrible position, Pavel. For which I apologize."
"Sir, you don't need to apologize."
"I rather think I do," Mr. Scott gently assures him. "Trust me, you did the absolute best you could in a completely fucked situation. Maybe better than I would have, and definitely not any worse. Anyone who says otherwise can answer to me, and the captain now that he's back in the waking world."
Pavel flings himself at the opportunity for a subject change. "Is he doing well, sir?"
"Well enough for me to give him a piece of my mind." Pavel is sure his horror is clear on his face, but the Chief looks unashamed, proud even. "Oh, he had it coming, after what he put all of us through. Plus, he's still pretty sedated, so I doubt he'll even remember a word I said."
Pavel blinks a handful of times, unable to conjure an image of anyone yelling at the captain. (Usually it's the captain doing the yelling at the commander, who is only ever placid and stoic in the face of it.) He says the first thing that comes to mind, since that's easy, and easy is about all he has the mental energy for. "I accept your apology, sir. And, if you could teach me more about engineering, maybe next time it will not go so bad."
"Good Lord, there'd better bloody well not be a next time," the Chief says, throwing his head back to stare at the ceiling. "But with that madman still our captain you're right, there probably will. You've got yourself a deal."
Pavel manages a weak smile. "Thank you, sir."
"Oh, don't go thanking me yet--the first opportunity I get, I'm leaving it all to you again so I can have some shore leave and get well and truly plastered."
His smile strengthens and feels more genuine. "Of course, sir."
When they return to the warp core installation, Pavel feels less afraid to think about the previous three weeks and where he fits into them.