The order is coming, Casey knows. It's only a matter of time before General Beckman orders him to kill Chuck, and Casey very much doubts the new Intersect will blow up just in the nick of time. So he makes preparations, gets ready, flushes out his head gear and brings his A-game to the table.
Over his headphones, he hears Chuck moving around the kitchen. From the clink of a knife against a jar, the rustle of a wrapper, the sound of the fridge door opening and closing, Casey knows he's making a sandwich. One of his favourite pastimes; something that requires his full attention.
Chuck doesn't hear Casey enter through the Morgan Door, doesn't hear him move down the hallway. He doesn't see Casey take a quick look around the corner because he's putting the butter back in the fridge. Casey is right behind him before he has chance to turn around, the needle going right through his thin trousers and into his buttock. He has time to yelp, then Casey is catching him for the very last time as he falls, lowering him gently to the kitchen floor.
Casey leaves the apartment the same way he entered, just as Ellie and Awesome walk in through the front door. Ellie does CPR while Awesome calls for an ambulance. Casey, a good neighbour to the last, comes over at the sound of the siren and drives Awesome to the hospital. Ellie is still doing CPR on Chuck in the ER when they arrive. It's forty minutes later that Awesome leads her away to let the attending doctor write down the time of death.
Ellie cries for a whole day.
The autopsy report says that Chuck died from Sudden Adult Death Syndrome. His heart simply stopped, probably weakened by a bout of flu he had a year ago.
The funeral is two days later. Sarah wears black, cries at the appropriate moment, and corners Casey after the service.
'Did you get the order? Was it you?' She's pale, trembling with the strain of holding herself together.
Casey shakes his head.
'I'd have used a gun. You saw the autopsy report. All the time we spent keeping the bad guys from shooting him, we couldn't protect him from his own body.' He sighs. 'Take some time off, Walker.'
Casey spends a little while removing the bugs he placed in the Bartowski's apartment, but lets the agencies 'sanitize' the Buy More. He only goes back in there to hand in his resignation because he's learned not to underestimate nerds. If he vanishes without a trace, they might just start digging into his background.
He packs up the apartment, takes some clothes, his bonsai, a couple of cases of weapons. The NSA clears out the rest of the apartment and, with the CIA, empties the secret spy base underneath Orange Orange. Twelve hours after the funeral, 'John Casey' is officially wrapped up.
He drives away from that little apartment complex without anyone noticing that he's gone, and he wonders how long it'll take before Ellie realises he's no longer around. He's pretty sure that Morgan will let her know Casey was so shocked by Chuck's untimely death that he decided to do some travelling, get more out of life than could be had selling appliances at the Buy More. It's a sign of how much being around Chuck has changed him that Casey hopes, very briefly, that Morgan gets out of the Buy More too. The little bearded freak will have to do all the living for the both of them now.
Casey stops his car at a little motel twenty miles down the road. He's already checked in under the name Guntersen, so he parks his car round the back where it won't be seen from the road, double-checks that the GPS tracker is turned off, and goes to his room where he sits on the bed and reads.
It's dark outside by the time Chuck wakes up.