Disclaimer: The respective owners own the Walking Dead and Buffy the Vampire Slayer, which is not me. This was written for entertainment.
Timeline: I'm making it July 2012 and TWD is at the start of season 2, BtVS is nine years after the end of S7, and I'm using certain things in the comic (so some spoilers to that. Though, warning, I've never read the comics).
Xander wondered, not for the first time, what he was doing. Well, he knew what he was doing, he was walking through the woods in the middle of nowhere, but he didn't know why. The world had basically ended after so many years fighting to prevent hell on earth, and it happened anyway. So Xander again questioned why he was even still fighting to survive. Everyone he knew and cared about was dead, and they were his reason to live and to fight, but now he had no one.
Xander was just tired. Sure, he was sad in the beginning and even angry, but after two months of wandering around alone, other than the undead to keep him company, he was just done. This was it for humanity, fight to survive or die and become the walking dead. There could be no more magic wand waving or even a wish for everything to be okay again because magic was dead, which was the cause for the whole mess.
When Buffy destroyed The Seed, she destroyed The Magic in the world- all the magic. Shortly after The Seed shattered The Magic started dying, and that included magic users and everyone else who was supernatural or otherworldly. They started getting sick with a high-fever until they eventually died. If only death were their problem, but no, the dead had to start waking up, and not in a vampirism sort of way, but in an animalistic-not-even-really-there-animated sort of way. Anyone who had died after The Seed broke woke up exactly 24 hours after the destruction of The Seed. The undead are just walking and groaning corpses whose only motivation is food, and their food of choice- the living. The undead didn't have to compete with vampires anymore since vampires and other demons just dusted away when the sickness was happening.
Xander actually witnessed the sudden dusting of a vampire, Angel to be exact. Xander had sat by Willow, one of the first to get sick, and watched as Angel slowly started to crumble away into dust. Xander was quite satisfied by Angel's permanent end of existence because he would have gladly done the deed himself.
The sickness had taken over about 85% of the Slayer Organization née Watchers Council, and everyone in the organization was panicking. After more deaths to their squads worldwide, Xander had been nominated to travel back to the States to give morale to the sick Slayers and other Council members. He didn't understand why he had been chosen to go, sure he was head watcher at their main HQ in Scotland and was well-known in the organization because of his friendship with Buffy, Willow, and Giles, but that didn't mean his presence was going to help people in the States any more than some other random person.
Xander agreed to go only because Willow told him to. He didn't like to think of it as her dying wish, but they both knew she was dying and that was why she wanted him to go so he didn't stay and watch her die.
Halfway through his flight to Cleveland he had received word of Willow's death through an e-mail. She was 37 out of 68 listed on a new e-mail notice that had been going out regularly since the sickness happened so The Slayer Organization members could keep track of who was sick and was dead.
Rosenberg, Willow expired 7:38 PM BST
Expired. Xander didn't know why the maker of the e-mail used the word expired instead of died, expired seemed so cold and strange to say, but those e-mails had been going around for more than 15 hours before that specific e-mail, and Xander supposed maybe the person just felt better saying expired after having to type who had died. Xander didn't really care either way; all he knew was that his Willow was gone. He didn't read Buffy or Dawn's name on that list so they were still alive around that time, hopefully.
Buffy had locked herself and Dawn away in a room once they figured out The Seed's destruction was the cause of the sickness. Xander assumed she wanted to get away from the blame, even though he didn't blame her for what was happening, well not much, didn't mean anyone else didn't, or that she didn't blame herself. So, Xander let Buffy have her little haven away from everyone because he had to be there for Willow. Though with Dawn and Buffy away from everyone Xander wondered if anyone was even checking on them. He himself didn't even check on them or say bye before he left. He had hovered outside the closed door for a few minutes, but he was too scared to open the door and see what was on the other side. Even if they were still alive they would look like death, and he didn't want his last memory of Dawn and Buffy to be of them sick or dead, he wanted his memory of them to be full of life. So Xander said bye to a door.
By the time Xander landed in Cleveland he had received 3 more e-mails, but he left them unopened. He had finally accepted the fact that he was being left behind again because he was too normal for the sickness to affect him. It was absurd to Xander to think of himself as normal still after everything he had been through, but no, he had been judged and found wanting by the sickness. Not magical enough, never special enough, and just not enough even for himself to keep on living.
And that's why Xander was in Nowhere, Georgia giving up.
Xander slipped the heavy hiking pack off his shoulders as he dropped the duffel full of weapons to the ground. He wouldn't actively kill himself like falling on his sword, but that didn't mean he wouldn't just sit down and wait for one of the dead to pass by.
Xander looked up through the trees to the falling light of the sun and again wondered if heaven was still up there or if it too died. Xander hoped that heaven was still there and that's where everyone was enjoying their paradise. He sometimes even hoped they were looking down at him and nagging at him, but at the same time, Xander knew if they were in heaven they would not be worried about Earth or him.
Xander was alone.
After years of doing what Xander did, Xander reacted without hesitation and immediately ran towards the shouted plea without a second thought. Xander quickly found the source of the scream; it was a child running from one of the reanimated dead close behind her.
The young girl spotted Xander ahead of her and nearly stopped running in his direction, but she seemed to think Xander was safer than the thing trying to eat her. Xander tightened his grip on the axe in his hand, his trusted and favorite axe was left behind in Scotland, but the fire axe hadn't left his side in two months and had gotten him through the warzone at the airport.
The undead now had its sight on Xander once the girl was behind Xander, but the thing was slow and the axe's blade quickly met its decomposing head. Xander pulled the axe free and watched the thing drop to the ground in a thud, and once satisfied that the thing was now dead-dead Xander scanned the surroundings. One undead usually met more undead, Xander noticed they liked to travel in packs, but after seeing no other movement and hearing no shuffling nearby Xander turned around to face the girl.
The young girl, who Xander guessed was no older than twelve, was about ten feet away from him and was about a spook away from running. Xander slowly crouched down and tried for a smile to soften his look. Xander knew he was a sight to see with his eye patch and dried blood and whatever else that accumulated on his person through the weeks traveling.
Xander watched as the girl watched him and when it looked like she wasn't going to do anything but stand there Xander made the first move by saying, "Hi."
Xander's soft greeting seemed to open the girl's vocal cords because she immediately responded with a quick, "I dropped my doll," before more words tumbled out of her mouth, "the walker chased me after I got lost, Mr. Grimes told me to hide and keep the sun to my left to get back to my mom. I just want my mama. Can you help me find my mom?"
The girl's babble-like words nearly brought a smile to Xander's face, he had been without human contact for weeks and it was refreshing to see and hear an innocent in a damned world. Xander didn't know what to think of the young girl's sudden appearance in his life, divine intervention he mused briefly when he remembered he was moments ago of just laying down to die. Xander wondered what it was about girls finding their way into his life and altering his life. He didn't know her name yet but she was more than likely going to find her name with the likes of Willow, Buffy, Cordelia, Anya, etc. who had changed his life for the better.
"Yes, I'll help you find your mom."
The girl visibly relaxed at Xander's confirmation to help her, and when Xander was sure she wasn't going to run if he moved Xander stood up from his crouched position.
The girl stepped a little closer to Xander and replied, "I'm Sophia."