Ani believes she is just an insignificant whisper of a girl in a loud world. This is what her mother tells her anyway. Her father made her feel important, but hes been off fighting in Spains Civil War, and his voice in her head is fading. Then she meets Mathias. His family has just moved to Guernica and hes as far from a whisper as a boy can be. Ani thinks Mathias is more like lightning. Mathiass father is part of a spy network and soon Ani finds herself helping him deliver messages to other members of the underground. For the first time, shes making a difference in the world.