Mystery of the Blue Ring — Patricia Reilly Giff

Emily Arrow's blue ring is missing. What could have happened to it? Dawn Bosco knows the whole class thinks she stole it, just because she borrowed Emily's unicorn once. But that was weeks ago.

With the detective kit her grandmother has given her -- a polka-dot hat and fake glasses with furry eyebrows -- Dawn rushes out to track down the crook. Can she find the thief -- and clear her name?