PART 1
The twins go back inside just as their mom calls. Dipper answers while Mabel talks to their dad, and tells his mom that he plans on staying in town for two weeks. He goes upstairs and accidentally walks in on Mabel as she is changing. Dipper insists on making a set of rules for the room to prevent something like that from happening again, much to Mabel's dismay. However, she can't say any of the rules don't work, and they go to bed.
As Dipper is getting dressed the next morning, he notices a figure with glowing red eyes watching him from the edge of the forest. He runs outside quickly, but the figure has disappeared just as Wendy arrives, and a quick search turns up nothing. The two go back inside to see Stan trying to clean up the coffee Dipper made him spill on himself.
After an impromptu dance party, Stan sends the twins in town to pick up food, supplies to fix up the building, and fake safety inspection certificates. Dipper insists on taking his car, but after he realizes he forgot his keys upstairs, and Soos breaks said stairs by dropping a penguin down them, Mabel takes great pleasure in scaring the daylights out of Dipper as they go into town on her bike.
They arrive at the Bargains Depot alive, and begin shopping around while telling one another about to the past year. Predictably, Dipper has been doing a lot of intellectual stuff. Less predictably, Mabel reveals that she has been taking martial arts. Dipper mentions how he told their mom two weeks, and even though both he and Mabel want to stay longer, they have important things back home. Mabel sees a figure that looks like 12-year-old Dipper walking around the store, but only sees him for a split second before he disappears.
The twins go back to the Shack and Dipper and Soos start fixing the roof while Mabel puts away the groceries. She and Wendy have a laugh about Dipper on the bike, and Wendy tells her that the summer will be better with them around. Mabel mentions Wendy's friends, but Wendy tells her that she and her friends have grown apart before Mabel throws glitter everywhere and changes the subject to her and Dipper being distant from each other. Wendy tells her to try and fix things as they come up as opposed to waiting around and/or trying to fix everything at once. Mabel again sees what looks like 12-year-old Dipper walking into the kitchen, but it again disappears, an open packet of a ramen-like product on the floor.
On the roof, Soos shows Dipper where Stan is planning on building motel rooms for people to spend the night in. Dipper is at first shocked that Stan would want people to stay, but once he realizes how much money Stan would make by doing so, he realizes that it actually makes sense before seeing the figure with red eyes again. He tries to show Soos, but it disappears a second time.
After the roof is finished, Dipper tells Mabel about the figure with red eyes, and Mabel tells him about the 12-year-old Dipper she has seen walking around. Mabel at first thinks it is the shapeshifter, but Dipper reminds her that he is froze underground, and tells her that he thinks it is a doppelganger trying to replace him. He says that light can weaken a doppelganger, and the two decide to try and stop it as soon as possible, Mabel insisting on calling the creature a Dipper-ganger.
PART 2
The twins put on bug spray, put new batteries in their flashlights, and get ready to head out, despite a storm coming and fog rolling in. They enter the woods and paranoia sets in, the fog making it hard to see and the storm causing a lot of noise. Dipper mentions their mom before Mabel disappears.
Mabel's disappearance was an attempt to lighten the mood by scaring Dipper, but it makes him upset and closed off. Mabel tells him to calm down and loosen up, and the two yell at each other before Dipper falls down a hill. Mabel quickly rushes down and finds Dipper. The two apologize and start heading back to the Shack, Dipper being attacked by bugs.
Meanwhile, the real Dipper wakes up to find a figure with glowing red eyes holding a spear to his face. The figure questions why Dipper hasn't shapeshifted yet, and Dipper tells him that he is human. The figure realizes who Dipper is and reveals himself to be a goblin named Sibs. Sibs leads Dipper to Goblitropolis, the Goblin's home, and introduces him to the Goblin Governor, Gig.
Gib tells Dipper that another Goblin, Strooder, is the figure with glowing red eyes Dipper has been seeing watching him from the forest. Dipper tells Gib that he and Mabel were looking from a doppelganger. Gib tells him that they don't know anything about a doppelganger, but they have been at war with a creature that can change its shape for the past two years. Dipper describes the man from Baron Num Num's Beans and realizes the the Shapeshifter is back just before Strooder and his team return.
Strooder reports that his team saw Mabel leaving with a person that looked like Dipper, and the two were heading back to the Mystery Shack. Gib gives Dipper a necklace that can freeze the Shapeshifter in whatever form it is currently in. Dipper starts running back to the Shack as the Goblins assemble a team to help capture the Shapeshifter.
Mabel and 'Dipper' are getting close to the Shack when Mabel realizes bugs are attacking 'Dipper,' despite all the bug spray he put on earlier. Mabel asks him several questions, and while he gets all the answers correct, she still feels like the Dipper with her is not her brother.
The two walk into the Shack, Wendy behind the counter as usual. The second she sees 'Dipper,' she knows something is up. She reminds them to put their boots outside, and 'Dipper' moves to obey, proving he is not real as there is no rule about no shoes in the building.
Wendy tries to attack him with a bat, but the Shapeshifter turns into Wendy and knocks her down. Mabel throws the bat at him, hitting him in the head. He turns into the Baron Num Num's man and mentions a power surge freed him from the freezing tube before Soos walks in and provides a small distraction. Wendy attempts to kick the Shapeshifter, but he grabs her leg and throws her out the window.
Stan comes to see what the commotion is about as Soos goes to check on Wendy and Mabel leads the Shapeshifter outside. Mabel is able to knock him down in his Baron Num Num's form, but then he copies her body and starts getting the upper hand.
Dipper arrives and grabs a branch as the two Mabel's start circling each other. The first mouths "You can do it" at him when they face each other. The second Mabel reaches into her pockets, yells POOF and throws sparkles and ramen everywhere. Dipper puts the Goblin necklace on the Shapeshifter, freezing him in Mabel's body.
The Shapeshifter moves to attack the twins when Soos and Wendy come out, a Goblin army coming out of the forest and closing in on him. The Shapeshifter tries to run into the Shack, but is met by Grunkle Stan with a gun. The Goblins capture the Shapeshifter and take him back into the woods.
Soos reveals that he met the Goblins when his car broke down, and he helped them establish their current society. Wendy tells Dipper what happened to her, but also says that she is completely fine, and everyone goes back inside as the Goblins leave.
After cleaning up the mess and fixing the window, the twins go upstairs to change and get in bed. Mabel realizes they broke several of Dipper's rules by changing in the same room at the same time. Dipper crumbles up his list of rules and the two go to sleep, not worried about small awkwardness compared to the day they just had.
Cryptogram:
19-8-1-16-5 25-15-21-18 6-15-18-13 20-15 2-18-5-1-11 20-8-5 14-15-18-13.
12-15-19-5 25-15-21-18 13-9-14-4 20-15 5-19-3-1-16-5 20-8-5 20-9-13-5.
23-8-1-20 23-9-12-12 25-15-21 2-5-14-4 20-15 18-21-14 6-18-15-13 20-8-5 5-14-4?
Shape your form to break the norm.
Lose your mind to escape the time.
What will you bend to run from the end?
