Warnings: Gore of the type that might be expected from a zombie frog.

Spoilers: No real spoilers, but written with Season 4 in mind.

Disclaimer: I don't own Fringe or its characters.

Author's note: Written for Halloween 2011.

The Hopping Dead

Astrid caught movement out of the corner of her eye, frog-shaped and green. Walter must have taken another bullfrog out and left it on the lab bench. She turned, ready to catch the poor thing and put it back with the rest, and froze. The frog croaked wheezily at her. The wheezy was understandable, given the intestines stretched out behind it; why it was croaking at all was the mystery. The last time she had seen that particular frog, it was splayed on the dissection tray three feet away, most decidedly dead.

"Walter," she called. She didn't yell, just projected her voice to be sure Walter would hear her. Once, she would have been fighting to keep her voice steady; now, all she fought was annoyance and the urge to roll her eyes. She refused to look away from the frog, however. If she looked away, it might move somewhere else, and she wouldn't know where to point Walter when she told him to get rid of it. Granted, finding the thing wouldn't be that difficult—a trail of blood and bits of viscera marked the frog's path from the dissection tray to the middle of the lab bench—but she felt better knowing where it was.

The frog croaked again and attempted a hop towards her that was more a lopsided stagger. Another few inches and it was in danger of falling to the floor. She took a step back; she didn't want frog guts splattered on her shoes if it fell. Especially not these frog guts.

"Walter," she called again, a little more urgently. "Get down here, now."

Too slow for her liking, Walter emerged from Gene's stall and wandered down the stairs. She stabbed a finger towards the frog. "What did we agree about leaving experiments around the lab?"

He hummed thoughtfully, shuffling forward and studying the frog. "That we would do our best to avoid it," he said. He picked up a probe and prodded the frog's head. It snapped at him, missing his fingers by centimeters. "A request which I attempt to honor."

"Except for the times you don't. Like this."

"That, my dear, wrongly presumes that I am responsible for reanimating this frog."

She narrowed her eyes. "So the frog just happened to reanimate?" Not that she hadn't seen weirder—three years with Fringe Division had cured her of the belief that anything was impossible—but she also didn't believe in coincidences. A man who was capable of giving temporary life to a dead bird was not only equally capable of giving temporary life to a dead frog, but the most likely culprit.

"Nothing just happens; there is always a cause. I was simply not the cause." He continued poking the frog. The frog continued to snap at him with surprising speed. After the first few repetitions, she realized the frog was not going after the probe which was poking it, but Walter's fingers. "Fascinating," he muttered. "The central nervous system was destroyed. Even reanimated, the frog should be incapable of both voluntary movement and sensory perception, and yet, clearly"—he again poked at the frog, and this time only excellent reflexes saved him from being bitten—"it is capable of both."

"Disgusting." She wrinkled her nose and grabbed a heavy glass bowl off the shelf next to her. She nudged Walter aside and carefully slipped the bowl upside down over the frog. It lunged the instant the bowl settled over it, hitting the clear glass with a hollow thump that shuddered through her hands. She left one hand pressed flat against the bowl, keeping it in place, and watched as the frog threw itself at the glass again. And again. And again.

Swallowing down her unease, she asked, "If you didn't do it, what did?"

He tapped the side of the bowl. "A virus, perhaps. Or a parasite. Something that is capable of both hijacking and controlling the nerves for its own purposes."

A thump came from the direction of the cold room. She glanced at the door to the room, just for a second, then back at the frog. They stored corpses in the cold room, a temporary holding facility until Walter took the samples he needed and the bodies could be shipped off to a more permanent location. The five bodies from their latest case still waited on transport.

"Depending on the mechanism," Walter said slowly, staring at the cold room, "the effects may not be limited to a single species."

Another thump came from the cold room, louder this time, followed by a rattle and what sounded like a moan.

"Olivia," Astrid yelled, reaching for her gun. "We have a problem."