The next morning, Soos was arriving at the Mystery Shack for his shift, still humming the same rock-and-roll tune to himself. Just at that moment, he spotted Wendy's hat lying on the ground close to the shack.

"Why is Wendy's hat lying here all alone?" Soos questioned, "Hey, Wendy? Are you nearby? You lost your hat!"

But his call went unanswered. Soos picked up the brown hat and knew that something was definitely not quite right. So he went right into the Mystery Shack's gift shop, where the three Pines family members were right then, and spoke out.

"Dudes!" he said, showing Wendy's hat, "It looks like we have another mystery on our hands!"

"Isn't that Wendy's usual hat?" asked Mabel, examining the cap, "Did you steal it from her, Soos?"

"No way, Mabel," said Soos, "I found it lying by itself in front of the Shack. I think she's gone missing."

"Missing you say?" said Stan, looking up from checking the register's money, "Oh boy, this is not good...who will be here to look after the register while no one else is around?"

"Wendy's...g-gone?!" stuttered Dipper, feeling very worried. "Wait a second..."

He began to remember back to last night. He was briefly woken up at midnight by what sounded like the panicked scream of Wendy, coming from far away in the distance. At first he thought he was dreaming it, but it seemed now that it was real. After explaining what he heard last night to the others, Dipper understood now that it all seemed to add up; the mysterious shriek of Wendy, the absence of her at the Mystery Shack and her hat laying there on the ground.

"Okay, gang, we should probably look around the yard for clues to Wendy's disappearance," commanded Dipper, immediately running outside to search for any evidence.

"Wow, he sure is determined," said Stan, following after him.

"Oh, Dipper, you and your crush on Wendy!" chuckled Mabel in her thoughts.

Soos, Dipper, Mabel and Stan were then searching around the grassy lawn area of the Shack, looking for any sort of clue to Wendy's vanishing since her hat was found in the area.

"Hey, dudes, look at this," said Soos, coming across something interesting in the grass.

He showed it to the Pineses. It looked like a dark green discarded scale, the size of an acorn, from what appeared to be some kind of Reptile.

"Hhhmmmm...It definitely looks like a piece from the body of something with scales," said Stan, "Sort of like what happens between my toes if I don't clean them often."

Soos and the twins just looked at Stan strangely for a moment and then went back to thinking.

"Hold on," said Dipper, snatching the scale from Soos and looking closely at it, "I-I think I've seen this before." He began remembering the detailed sketch of the Giant Mountain Gargoyle that he read about in the mysterious journal yesterday.

"Mabel, come on," said the boy to his sister, "We've got secret research to do."

"Alright, Dipper!" said Mabel happily, following her brother back into the Shack and up to their bedroom while Soos and Stan deciding to keep looking for more clues.

Back up in the bedroom, Dipper showed Mabel the journal's information on Giant Mountain Gargoyles, also finding the discarded scale to be a perfect match to the minor journal sketch about the scales of the large and elusive beast.

"It looks like Wendy's been kidnapped by some big Gargoyle from the mountains!" said Mabel in surprise, believing this to be the case of Wendy's disappearance.

"Maybe that is it," said Dipper, now pacing around in a circle while in thought, "but if that's true, then what would it want with Wendy?"

Meanwhile, in the mysterious creature's cave up in the high mountains, Wendy was waking up. She found herself to be tied to a large stalactite with vine-like Plants, close to the mouth of the cave where she could see the open sky outside. Plus, she noticed that her hat was missing.

"Yep, this is totally not a dream," said Wendy, twitching around to get free from the tight vines grip, but to no avail. "Can someone tell me what's happening here?"

"It is about time you knew the truth, Human," spoke a deep voice from the shadows. Out of the darkness and into the light (being shown from the sun shining through the cave's entrance) came, breathing deeply, a large male Giant Mountain Gargoyle, measuring 24 feet long from snout to tail, 7 feet tall to the shoulder, his yellow eyes focused right on Wendy.

"Oh no! Wh-who or what a-are you?" spoke Wendy, feeling quite afraid, her eyes widening in fear.

"I am a Giant Mountain Gargoyle," the great Reptile responded, "I am one of the few remaining members of my species. My kind does not give each other personal names like you humanoids do, but I have gone by many. You may call me Efferus."

"Okay, sure...Efferus," said Wendy, not sure how to get her way out of this situation, "Now, what do you want me for?"

"What I want from you is something quite special," responded Efferus, now rearing up on his hind legs to look the girl straight in the eye while she was tied to the stalactite. "You see, as I have told you, my species is quite rare, and I have heard that there is a more magnificent way to bring them all back in greater numbers. It will require several different ingredients, most of which I already collected. Now, you have within yourself the last ingredient on the list...the heart of a standard female Human...your heart..."

"If you're going to do that," said Wendy, jokingly, despite her fear, "then you're going to have to take me out to dinner first."

"NO! You fool!," snarled Efferus, "I speak of the muscular organ that pulses blood through your body."

Wendy gulped in great fear. "Look, I-I-I'm sorry that most of your kind is gone, b-b-but do you r-really have to take away my h-h-heart?

"Only the heart of an adolescent Human female with your precise color of hair and at the exact age of 15 summers old," replied Efferus, "And you are more than perfect. And few can save you now, for I sense the darkness beginning to spread out there..."

"Oh man, this big guy's been doing his homework!" Wendy said in her thoughts nervously, speechless to the fact that she was a Human girl with all the traits needed for this project.

After mentioning the mysterious subject about a sort of darkness out there, Efferus went over to a large stone bowl he had carved, making sure all the other ingredients (being mainly different leaves and bones from smaller Animals) for his concoction were in place. He now began to add them to the bowl.

Wendy knew that she was in way over her head with this situation. All she could do was hope for a miracle to help her, like the arrival of her friends to come and save her from this winged beast. Unknown to her at the moment, her friends from the Mystery Shack were already on their way to find her, heading through the forest to reach to distant mountains on time.