One paragraph plot summary : On the ancient site of Pompeii where it attracts tourists around the world, an ancient dress like Roman guy is disturbing tourists. On the other day, the Mystery Incorporated gang's arriving and they start to learn about those disturbance. Then they investigate and get a lot of clues after being chased by that guy. Step by step, they uncover the truth behind those disturbances.
This episode 12 is a little bit boring. I was nearly falling asleep. But it's not that bad either. At least, I could finish it. Maybe because I'm not interested in Pompeii or whatever ancient. That's why I felt like that. That being said, the motive is so clear. In some of the episodes, the motive of why the disturbances are keeping to happen. But in this one, it's so crystal clear. This is the only one thing that is good of this episode.
All in all, although it's a bit boring, but it's not that much. If they've made it less boring, I think it'd be better. I really hope that the next episodes will not be like this.