- 4 AM: 6 DAYS EARLIER -

"DAPHNE! VELMA!"

Fred and Shaggy sprinted as fast as they could back to Cabin 13, their breath coming in cloudy plumes. They could hear the girls' screams for help tearing through the air.

"Like, where are they?" Shaggy cried, as he ran frantically around the cabin.

Fred immediately stopped in his tracks and pointed to the cabin's small window. The lights were on. Fred could hear growling.

"Shag, they're in there! The bedroom!" He waved his hands frantically, trying to get their attention, but the cabin's foundation was high off the ground – he could barely reach the window's ledge.

Shaggy, being much taller, managed to slam his fists against the window in a final attempt to garner the girls' attention. "Guys!"

And then Velma and Daphne appeared at the window, their faces pale. They shouted something, but the window's thick glass muffled their words.

"We need to get in there!" Fred cried as he ran to the front door. He tried the handle. Locked.

Shaggy hesitated. "What if it's that shadow?"

Fred whirled to face him, his eyes wild. "Do you want them to die?"

"No!"

"Then get over here and help me!"

They both threw their shoulders against the door. It didn't budge.

Then they heard louder barking and growling. It was closer. It was coming from the inside.

Shaggy felt his heart pound against his chest. "Like, is that –

"It's Scooby," Fred said, unable to believe the words coming out of his mouth. "I think . . . I think he's got them trapped in the bedroom."

Shaggy shook his head. "No way, man. Scooby wouldn't –

"Just help me break this down!" Fred cried, gesturing to the door. "On the count of three, we kick down the door. One . . . Two . . . THREE!"

The door burst open, still hanging onto its hinges. And they were in.

A guttural growl ripped through the room. Scooby was scratching at the bedroom door, his mouth foaming and his eyes unrecognizable.

Shaggy's stomach dropped to the floor. His breath caught in his throat. "Scooby-Doo?"

The only response was an aggressive growl that sent a wave of vibrations through Shaggy's body.

Then Scooby lunged.

Shaggy managed to dive out of the way just in time. Scooby flew past him, right through the front door. But he wasn't done.

Fred reacted fast, slamming the door shut. But it was weak, barely holding after they broke it down. He braced himself, feeling the force of Scooby throwing his body against it.

Shaggy was trembling, frozen on the floor. This was his best friend.

But this wasn't Scooby.

Fred's voice brought him back. "Shag! Snap out of it! Get the girls!"

Still shaking, Shaggy pushed himself back to his feet, his elbow throbbing from the fall. He staggered to the bedroom door and knocked on it rapidly.

"Like, it's me! Open up!"

Velma opened it, holding a bedside lamp, ready to swing at anything that came through the door. But the second she saw Shaggy, she dropped it to the floor. Daphne was standing in a corner of the room, trembling.

Shaggy's chest tightened and his stomach churned.

His best friend did this to them.

Something – or someone – did this to Scooby.

Shaggy swallowed, his voice hoarse. "Wh – What happened?"

They didn't answer at first. They were just as unable to comprehend the situation as he was.

"Guys?"

Daphne's lips parted, but no words came out. She didn't want to tell Shaggy what happened. Nor did Velma. Scooby was his dog. They'd been through everything together. How could they tell Shaggy that his best friend attacked them?

Velma spoke first. "He – he was fine at first, but then he just . . . wasn't."

The banging on the front door was getting louder. Fred began to struggle. "We don't have time for this! Shaggy, help me!"

"He – He tried to bite Velma," Daphne whispered, her face pale. "Shaggy, it wasn't him."

Shaggy didn't know what to say. What to think. What to do. He just stood there, his mind in a fog.

Another violent SLAM rang through the cabin. "Shag! Help me!"

Snapping out of his daze, Shaggy rushed forward and pressed his weight against the door.

Velma and Daphne ran to join them.

"He wasn't speaking, either," Velma added. "Not a single word."

Daphne shuddered. "It was almost like . . ." her voice trailed off, afraid to say what she was thinking.

Velma finished for her. ". . . Like he was just a dog."

Shaggy sank to the floor, his back against the door.

This wasn't Scooby anymore.

Then, there was silence. The banging ceased.

Velma peered through the window. "He's . . . running into the woods . . ."

Without a word, Shaggy pushed past Fred and stumbled outside.

"Scooby?"

But Scooby was gone.

Shaggy fell to his knees. And screamed what came into his mind, the sound echoing through the trees:

"SCOOBY-DOO! WHERE ARE YOU?"