On September 6, 2007, an African Grey parrot named Alex died prematurely at age thirty-one. For thirty years he and his owner, Irene Pepperberg, had worked together - two pioneers who opened an unprecedented window into the hidden yet vast world of animal minds. Over the years, Alex had proved many things. He could add. He could sound out words. He understood concepts like bigger, smaller, more, fewer, and none. He was capable of thought and intention. Together, Alex and Irene uncovered a startling reality: We live in a world populated by thinking, conscious creatures. Yet there was a side to their relationship that never made the papers. They were emotionally connected to one another. They shared a deep bond far beyond science. The story of their thirty-year adventure is equally a landmark of scientific achievement and of an unforgettable human-animal bond.