Prologue

A bird flew from a branch as a voice echoed through the misty forest. "We have everything? Water bottles, walkie-talkies, snacks, ear protection, first-aid kits and tools. Ok, guys, remember, if anybody sees anything, you have to call the rest of us immediately!"

Dipper Pines stood in front of his co workers and family, gesturing to the woods behind him. "We all know there's a giant bird in there somewhere, and we're going to find it!" Soos nodded seriously, pulling back his hat, while Mabel grinned and flicked her flashlight on and off again. Wendy Corduroy was smiling, clearly pumped for the impending search.

"Remember, we meet back here in an hour," the young detective reminded them. He slung his backpack over his shoulder and held a hand up to his forehead in a salute. "Let's find this thing!"

"Yeah!" Mabel cheered. She waved goodbye to her friends and brother as all four set off in their designated directions. Dipper waved back, tapping his book through his vest as he entered the woods. He felt like he could fly, almost. They had been planning the expedition for what seemed like forever.

Perhaps a week ago, Soos and Wendy had spotted a gargantuan bird soaring over towards the woods at the far edge of town. They had rushed to the Mystery Shack and told Dipper, who immediately started doing research on whatever the thing was. After three hours of obsessively pouring through his journal, the boy concluded that the animal had to have been a thunderbird, as there were no other mammoth avians in the area. Of course, the pair who had originally spotted the creature were eager to investigate it again.

The plan was to go thunderbird-hunting on the upcoming Friday of the week, just as Wendy finished her cashier shift. They would each go in different directions, as to better cover the massive territory the bird lived in. Several giddy hours of waiting later and they were all ready to go.

Dipper smiled to himself as he walked through the woods, flipping on his flashlight. Man, it sure was misty. Not to mention cloudy. He supposed it was good that there was a storm coming, as it either signified the presence of the thunderbird or attracted it. He still wasn't exactly sure about that entire thing.

He heard thunder rumbling in the mountains just a mile from the path he was walking on. "Should be close," he murmured to himself, scanning the woods and blinking at the dim light. The fog tickled his bare arms slightly and he hugged the journal closer to his chest. Damp would only damage the fragile pages further.

The sky got slightly darker as the boy made his way deeper into the humid forest. It had to have been thirty minutes since he had left the others. Twenty? Why hadn't any of them called yet? Where were they? Slowly, he started to feel a sense of timidity at being completely alone creeping through his body. It was so dark in the dense trees. He wanted to go somewhere brighter.

Suddenly, Dipper felt his heart leaping as he spotted a dark figure in the trees. It was racing towards him, as though it were made of mist itself. He let out an undignified shriek as he snapped to attention and started to race away in terror. A loud hiss came from behind him, and the air was torn from his lungs in panic.

The creature, whatever it was, was getting faster. Dipper increased his pace to an all-out sprint, running as fast as he possibly could. He curved his path, turning sharply again and again in hopes of losing his mysterious pursuer. To his utter relief, the thing seemed discouraged and disappeared into the woods.

Dipper slowed to a halt. Adrenaline still pumped through his veins, but he was struggling to get in air. The exhausted boy flopped to the ground and coughed, wiping the massive sheen of sweat from his forehead. What was that thing?

After lying on the ground for several minutes, he rose to his feet and began stumbling back the way he came. It took him a while to find the path, but when he eventually did, he barely felt any emotion. He was worn out. Maybe he should radio Wendy or Soos and ask them to come get him.

That was, of course, before he heard an earth-shattering scream.

Mabel.

Dipper started to run back down the path, ignoring his screaming muscles. That noise had come from the direction the creature had been going. The air entering his lungs seemed to get caught as he tripped over fallen trees and roots, gasping for air and at the same time crying out his sister's name.

"Mabel? Mabel?!" His frantic calls were getting weaker, but no less worried. He let out a cry of pain as he fell completely over a rotting tree trunk, tumbling into a ravine. Dipper rolled to a halt and took a second to catch his breath before forcing himself upright once again.

His heart could have stopped when he heard the response. "DIPPER! HE-"

His blood ran cold. His sister had been in pain. Slowly, an icy fire surged through him, filling him with furious energy. He bolted through the trees, not daring to stop for anything or any reason. Dipper was angry, hurt, terrified beyond belief, and now almost mindless. The fury at the thought of his other half being harmed fueled him.

A stream splayed out before him. Dipper slowed, wincing at the freezing cold of the water. The mist here was colder, too. Everything felt like ice. Ice was coating his skin, his eyes, freezing over his nose and mouth and muscles. It trickled into icicles in his hair and froze around his shins as he climbed out of the water. His body felt like it had been submerged in the arctic sea. He shivered as he started to pick up speed again, clambering over rocks as the scene changed.

The thick pine trees he had been racing through minutes before were thinning out, giving way to rocks and sandy earth. Dipper realized this was where Mabel had been searching. She had said she was going to look in the ravines before the mountains, because "Big birds like rocky places and I might get to see a nest of chicks". He was both relieved and horrified by this.

Underbrush became more scrubby and trees disappeared entirely as he burst out into the open, yelling his sister's name. The rocks dropped off steeply, leaving a giant gash in the cliff. Dipper whipped his head around frantically, scanning the landscape and feeling utter hopelessness starting to overwhelm him.

That was, of course, until he saw her body.

"Mabel!" he shouted, tripping over the rough terrain and rushing down the rocks to where she lay. He let out a yelp as the stones gave and he slipped uncontrollably down into the ravine. Battered and bruised, he pulled himself up to his feet and raced towards her, ignoring the bloody scrape on his knee.

His sister rested in a relaxed position, lying on her side with her arms splayed out and legs stretched. Most people would consider this impractical for relaxing, but living with Mabel since the womb taught him that she cared not for practicality. He stumbled down to his knees and started to shake her body, feeling terror rip through him once again. She must be injured, if she was unconscious.

He gazed over her fluffy green sweater with a grinning eagle on it giving a thumb's up. There wasn't any evidence of blood or trauma. Her legs seemed completely intact, and her head just as clean and glittery as it had been an hour ago. She didn't look like she was in pain. Her expression was blank. What was wrong with her? Why wouldn't she wake up?

The thunder boomed again, and Dipper blinked as a drop of rain landed on his nose. He shook his sister harder. "Mabel, wake up! Come on, stop fooling around." He blinked at her skin, suddenly seeming far more pale than it had been previously. The redness usually present in her cheeks was barely visible. He touched her hand, which hung limp and lifeless in his fingers.

Slowly, a terrible realization dawned on Dipper. "No, no, Mabel, get up, get up!" he shouted. "What happened? Why are you like this? You aren't…" He trailed off. Gently he took her by the shoulders and lowered his ear to her chest, pressing as hard as he could through her sweater. He didn't hear anything.

"No. No."

Dipper fell on all fours, cradling Mabel in his arms. It felt as though everything were being sucked out of him. "No, Mabel, Mabel, please. Please, please, just move or say something or…" The rest of the air in his lungs refused to form words as he started to sob. "No!"

His scream echoed through the woods, but he didn't even notice it bouncing off the rocky walls of the canyon. Mabel, young artist, awesome extraordinaire and bubbly optimist, wasn't breathing or moving or talking or anything. She wasn't stealing his hat, or drawing on his face with Wendy while he slept, or covering his clothes in glitter. She wasn't sitting by his side on the long evenings where everyone had gone home and he felt hopeless. She wasn't making him smile, or hugging him tearfully when he needed reassurance, or making him feel like the best brother ever. She was just lying there. Still warm.

Out of the corner of his eye, Dipper saw movement at the top of the ravine, but he paid no mind. He buried his face in his sister's hair, sobbing and yelling. She was gone. She was gone. She couldn't be gone, but she was.

He felt a gentle hand on his shoulder. Blinking and choking, he briefly turned his head to see the horrified face of Wendy. "What… What happened…?"

The young detective couldn't speak. He simply gestured at his lifeless sister, gulping in air and struggling to see through the stinging that was tears. Wendy slowly lowered herself to the ground, touching the girl's face in frantic disbelief. He felt as though everything was crumbling around him as his best friend, tall and strong and sturdy, began to cry with him.

The three lay there in the canyon, two staring at the other in grief while rain slowly began to seep from the clouds. They were now silent, locked in a state of anger and fear and sorrow. They stayed that way until they were found by the last member of the thunderbird hunting party, who had been wandering around for hours looking for them. There they stood. Three alive and grieving, and one gone.

A/N: Well, here it is! I have the cover up on deviantart, if you want to see it. Poor, poor Mabel...

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