"It wasn't out this morning." Kahlia says.
With her tools in hand, Hariel is able to disable the magical trap set in the lock, and, with a couple minutes of work, she is able to open the lock, which contains another book, which looks to be written in Lord Alistair's hand, but doesn't seem to make much sense to her. (Search to find the trap; Disable Device to get rid of it; take 20 on Open Lock to pop the lock; the book you find is either in a language you're unfamiliar with, or in some kind of code)