In the first episode of a three-part story, Niles (David Hyde Pierce) becomes convinced that his toothache is merely a "referred pain," and that he may actually have a heart condition. Well, maybe he didn't have one at the beginning of the episode, but he sure has one by fade-out time -- and it may all be the result of his own feverish imagination. Elsewhere, Frasier (Kelsey Grammer) has a bad feeing about the "terrific" new caregiver (Ana Gasteyer) hired by Martin (John Mahoney). ~ Rovi