Hugo Archibald is a doctor and brings home a wide variety of exotic animal species. The latest animal he brings home is a chimpanzee named Jennie. Dr. Archibald is not home very much, and Andrew feels he does not care about him. And Lea his wife does not want Jennie, and says she makes trouble. But the children take an instant liking to her. Jennie is unique in that she is learning to use and understand sign language. Jennie becomes an important part of Archibald family and Dr. Archibald's son, Andrew develops a close relationship with her. Jennie loves the things Andrew does, such as baseball and comic books. Jennie is also there for Andrew when he and his father disagree. A doctor Pamela Prentiss starts training with Jennie. She does not agree with the way Jennie is being cared for, and is seen as being rude to the Archibald family. She teaches Jennie sign language in a way that Jennie does not understand, but Lea finds a way she understands.