When a powerful new weapon threatens the spherical planet of Ringworld, a protector, an exile with the ability to speak with animals, and a native with a myster... » 

When a powerful new weapon threatens the spherical planet of Ringworld, a protector, an exile with the ability to speak with animals, and a native with a mysterious past assist explorer Louis Wu on his quest to save Ringworld from interplanetary war. Reprint. «