The Flame Alphabet (Vintage Contemporaries)

 
In The Flame Alphabet, the most maniacally gifted writer of our generation delivers a novel about how far we will go in order to protect our loved ones.
 
The sound of children's speech has become lethal. In the park, adults wither beneath the powerful screams of their offspring. For young parents Sam and Claire, it seems their only means of survival is to flee from their daughter, Esther. But they find it isn't so easy to leave someone you love, even as they waste away from her malevolent speech. On the eve of their departure, Claire mysteriously disappears, and Sam, determined to find a cure for this new toxic language, presses on alone into a foreign world to try to save his family.