One night, Emmy's sock flies off her foot and out of her bedroom window! So begins a fascinating adventure. On her quest to get her sock back, Emmy meets stars and planets, before finally coming face to face with the thief who stole her sock: a black hole!

At the end of the book, curious readers can access four pages of information on the science behind black holes! It explains in simple terms what black holes are, what really happens to Emmy's sock and how come she is able to get it back again (although it is a little worse for wear).