In "Scary-oke," after reciting an incantation from Journal 3 in an attempt to prove to Agent Powers and Agent Trigger that its contents are real, Dipper unintentionally raises the undead. With no way to defeat them, he and Mabel retreat into the Mystery Shack, and eventually meet up with Stan. The three are forced to hide in the attic and barricade the door to keep the undead out. Dipper then searches the journal once more, even though it said that the undead were unbeatable. However, under the UV-A rays of the black lights set up for the party, a hidden passage is revealed, having been written in invisible ink, revealing the zombie's weakness. After saving the Mystery Shack from the undead, Dipper pulls out a portable black light to view some of the journal's other hidden content. Having discovered that the journal has more information in it that's written in invisible ink, Dipper looks into more of its hidden secrets.
In "Into the Bunker," Dipper finds the location of The Author's secret bunker. When going to explore the bunker, he brings Mabel, Soos, and Wendy with him, and he uses his portable black light to show them the hidden drawing of a spiral staircase drawn onto the picture of the fake tree he first found the journal in.
In "Sock Opera" Dipper sits in his room with all of the lights off and the black light on so that he can investigate the hidden messages in the journal in hopes of figuring out the password to unlock the laptop.
When the Northwest family is preparing for their annual party in "Northwest Mansion Mystery," a haunting occurs in their home. Needing someone to stop the haunting, Pacifica Northwest approaches Dipper and asks for his assistance. The next day, while investigating the haunting, Dipper and Pacifica are cornered by the ghost. Realizing that it is a Category 10, Dipper looks through the journal and gets to the passage on Category 10 ghosts. Underneath the "advice" column, nothing is written, but Dipper pulls out the black light to reveal the hidden contents. Unfortunately, the only thing that is written is "Pray for mercy!"
In "Not What He Seems," upon discovering the other two journals in Stan's underground laboratory, Dipper uses the black light to reveal the warning written in the journals regarding the universe portal.
- 201. "Scary-oke"
- 202. "Into the Bunker"
- 204. "Sock Opera"
- 206. "Little Gift Shop of Horrors"
- 210. "Northwest Mansion Mystery"
- 211. "Not What He Seems"
- 218. "Weirdmageddon Part 1"
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