In 1971, graduate student Penny Patterson began teaching sign language to a gorilla named Koko, a scientific experiment that evolved into an intimate friendship lasting almost half a century and changed the course of human-animal communication.

The real life experience of Koko, a gorilla in California who uses sign language, with a young kitten whom she loved and grieved over when it died.

The author records her visit with Koko, a young gorilla in California who uses sign language and who experiences many of the same feelings a child feels.