About 20 million Americans suffer from some type of anxiety disorder. Many must deal every day with the fear that at any moment they could be overwhelmed by panic, one of type of anxiety disorder. The symptoms can be overwhelming. "My legs get shaky," says Theresa Murphy, explaining her panic attacks. "I can't control my own body. Everything gets blurry. But when it actually blacks out, and you can't see anything, that's probably the scariest thing." Episodes can last for a few minutes or days, she says. 48 Hours explores anxiety disorders and spends time with several people, including Donny Osmond, who are trying to overcome them. Correspondent Peter Van Sant reports on two people trying out a new treatment for panic disorder. Can one week of intense therapy erase years of anxiety? Find out. Although he has performed before large audiences for most of his life, Donny Osmond didn't know until recently that he had a severe anxiety disorder. Harold Dow finds out how Osmond faced his problem. Richard Schlesinger reports on a new method of confronting anxiety: using dogs as stress-busters.