It is time for Leoncillo, Carrasquina and Glayito, three cats of the Clan del Trueno, to become warrior apprentices. The three kittens have shown cleverness and the required strength, and everything points to them becoming prominent warriors in the clan. However, the three will become mixed in a dark secret, and an old prophecy foretells the coming of hard days, in which resentment and animosity against cats born outside of the clans will grow.