Artemis Fowl

I have already finished the whole book.

In this book of of three main protagonist is also Captain Short from the People civilization who is sent for the mission to clean the mess what Artemis Fowl has caused. She is one of the fairies. The fairies have their magic but it needs to be maintained by a regular ritual. The ritual must take place by an ancient oak because the acorn from the oak when sprinkled with piece of soil gives the fairy her power and magic abilities. 

One of the obstacles Captain Short faced was when she was imprisoned and very weak. Then she remembered  that she has got one of the acorns in her shoes. But the room where she is prisoned in is made of concrete. The way she got out from there was that she has been slamming her bed into the cement floor for many times till some soil showed out of the floor under the cement. Then she could sprinkle the acorn with this tiny bit of soil and she regained again her power. She became strong again and found her way out of the prison. She tricked Julia, her supervisor, by putting a spell on her where Julia stayed glued to the fake TV on the wall.