Signals: Looking for Visual Clues

French-born David says his dog obeys human speech, but it's clear he is signaling the commands to the dog. Mary goes to Sea World in San Diego, where Chuck Thompkins shows the hand signals he uses in his show with Shamu. In France, Mary gains insight on visual telephones. FILM INSERTS: Ways to say hello; animal sounds; uses of the X symbol. THE BLOODHOUND GANG: "The Case of the Human Whale, Part Two." The gang uncovers the identities of both their client and the man he seeks.