Look, in the second passage, the word catacombs is underlined in red.
5 seconds sound clip from Scooby-Doo, Where Are You! - Hassle in the Castle (S1E3).
You can hear this line at 00:10:17.689 in the Blu-ray version of the episode.
Quote context
[...]
- Hey, there's some writing on it. It says, Second passage of the old bell.
- There's no old bell in this old castle.
- Hmm.
- I've got it. The word passage must mean a passage in a book.
- Then The Old Bell must be the name of a book!
- And the best place to find a book is in the library.
- Well, this is the book called The Old Bell.
- Look, in the second passage, the word catacombs is underlined in red.
- And if my knowledge of history is correct, we should find catacombs in the basement.
- Okay, Scooby. Go in and take a look around. We'll keep watch out here. No, I'm not kidding.
- There he goes again with his fake-wounded routine.
[...]