BEFORE:

When Penny stumbled upon Sheldon and Leonard's stockpile of non-pershiable food items, blunt instruments, and guns, she nearly laughed herself out of the apartment.

"It's our zombie survival stash," Leonard explained, turning slightly red in the face as his embarrassment got the best of him. Sheldon, on the other hand, stayed entirely stone-faced as he calmly announced,

"It's an important thing to have, Penny. When the zombies come, will you be ready?"

It didn't matter that she had more experience with guns – real guns – then them, Raj, and Howard put together, or that she was the best shot. It still seemed weird that these two nerds with no real life experience – who's biggest violent threat involved wedgies and swirlies – would stockpile weapons. Even if it was for an event that would never happen.

"I figured I'd come stay with you guys." She grinned. Leonard gave her a sloppy smile. In his mind, he would arrive just in time to save her from the zombie invasion, snatch her hand while the hoards descended, and they would both run to safety, just in time to have hot, end-of-the-world sex on his kitchen floor. After securing the exits, of course.

Sheldon just gave her an approving nod.

"That's the best course of action. Of anyone in this building, we are by far the most prepared, and you wouldn't last ten minutes on your own over there."

Coming from him, it was practically a compliment.

THE BEGINNING:

Penny awoke to the sound of a scream. One shrill scream that seemed to last a good ten seconds before the body that carried it numbed over with shock and crumpled to the ground. At first, she thought she was dreaming. Back home, screaming was definitely not uncommon, especially at night when the bars let out and all the drunks stumbled home to their angry families. Even screams of horror were sadly not too foreign to her ears. This one rattled her out of a deep sleep, however, enough to have her pulling the covers a bit tighter around her chin.

A half an hour went by and silence crept over the scene just enough to tug her gently into a lulled, half-asleep state again. Then the jarring crunch of breaking class ripped the silence open again, and Penny gave up on trying to sleep. She threw the covers off her bed in a huff, ignoring the nagging fear that tugged at the back of her mind, and crossed the hallway to Sheldon and Leonard's apartment.

These weren't her normal friendly knocks. Oh no, she banged on their door. It wasn't that she was mad at them, just pissed off that she had a long day at the Cheesecake Factory tomorrow, and the street dramatics were thoroughly pissing her off.

"Sheldon! Leonard!" she barked into the eerie quiet.

Whatever else happened, she wouldn't admit that she had knocked on their door in the middle of the night because she was scared to be alone. There was some shuffling behind the door, a loud thunk followed by a very colorful word uttered by Leonard, and then more shuffling.

"Penny?" A voice tinted with fear called softly through the door.
"Yes it's me. Who else would be knocking on your door at 2:00 am?"

A series of locks clicked open with pops, and then the door crept open just a crack. Leonard's pale face peered back at her. Immediately, all her anger at the night drained away. She'd seen him look nervous plenty of times - the terrified mask of a nerd about to enter into an intimate social situation - but never like this. This was entirely different.
"Sweetie, what's wrong?"

He pulled the door open slowly, stuck his head out, and peered down the stairwell. His hand flopped aimlessly back and forth as he waved her forward.
"You'd better come inside." he murmured. The minute she was through the door frame, he went about locking everything up again. Penny hadn't remembered them having so many locks on the door before.

"What's going on? You look like you've seen a ghost." she touched his shoulder gently, rubbing in slow circles across the flannel of his nightgown.
Without a word, he pointed towards the window.

"We need to board that up." He muttered to himself. She moved across the room silently, then peered down into the street. In the harsh orange glow of the street lamps, she saw him. His skin adapted a strange, ethereal glow against the florescence of the lights. It took her a long moment to realize exactly what she was witnessing. Below the seemingly heaving man lay a woman, eyes open and glassy, with blood splashed on her face. Penny had seen too many cop dramas to know a dead person when she saw one. What she wasn't expecting, however, was the manner of her death.

As the man pulled away from her body, Penny caught a glimpse of the strings of flesh and blood that dangled from his mouth. Her blood looked brown, leaking slowly into the cracks of the pavement. He was eating her, ripping the guts from her stomach and shoving them into his mouth with grunts akin to an animal, caught in a frenzy.

He had no perception of his surroundings, of the woman that watched him from the third floor window, of the blue eyes that stared past him into death itself. He knew only the sweet taste of blood as it leaked into his own dying body, and his insatiable need to feed.

"Oh my God." Penny whispered. Her first reaction should have been to vomit, but she was in too much shock. It wasn't real. It couldn't be. In the distance, another window shattered into fragments, and a car alarm screeched a warning to the neighborhood.

"What the hell is going on?"
The sound of a rifle being cocked made them both jump. They looked over to see Sheldon step out of the hallway, hunting rifle in hand, and a look of fierce determination on his face.

His voice was gravel as he whispered,
"It's starting."