In this sequel to Chocky a year has passed since Matthew said goodbye to his alien friend. With the arrival of the summer holidays Matthew goes to visit his aunt in the countryside. While exploring he meets Albertine, a young mathematical prodigy. They soon become friends and discover they can communicate telepathically. One day Chocky returns to warn Matthew that they are both in danger. Matthew realises where the danger must lay - a scientist who wants to test Albertine's exceptional abilities. When he goes to warn her he finds she has disappeared. Matthew needs help but where is Chocky?