" When a rat sneaks in, there’s no way of getting rid of it. You give it poison, and it eats it. You set up a rat trap, and it shits on it. A rat is the most difficult thing in the world to get rid of. Because rats are cowards. Because they hide. Because they think they’re cleverer than you. "

― Carlos Ruiz Zafón , El laberinto de los espíritus (El cementerio de los libros olvidados, #4)