Use rhymes to solve this one.

* Bee: tree, 3, knee 
* Snail: pail, grail (the cup), nail 
* Dog: frog, log, hog 
* Book: cook, rook (chess piece), hook

You'll find pearls inside the locked puzzle box, which you have to examine.
Bring the magnifying glass over the pearls until you find a flawed-looking 
one. Hold the glass over it for a few seconds to register a clue.