Sly Cooper: Those rats got pegged.
Bentley: Raleigh appeared to have booby-trapped this entire place.
Sly Cooper: I'm going to enjoy this.
― Upon entering the library[src]
Upon entering Raleigh's library, Sly came across a booby-trapped rug and saw some rats being struck by two dart machines. Bentley believed that Raleigh may have set up these up to protect the treasure key. Sitting right below Sly was a wooden barrel, which he believed could provide some protection, though Bentley was not so positive about it, believing it seemed a little risky and very unsanitary, but there was only one way to find out.
There are 30 clue bottles to collect in this level, and the vault is located on the second floor, on the other side of the bookshelf with the ladder, right after the first two spotlights. The vault's combination is 2-4-2.
With the help of a straightedge and compass, the answer was simple. Dial in 2-4-2.