Gillian Holroyd (Kim Novak) is a modern-day witch living in Greenwich Village. A publisher named Shep Henderson (James Stewart) moves into the apartment above hers and she becomes interested in him. When she learns he is going to marry her college nemesis, Merle Kittridge (Janice Rule), the next day, Gillian uses her cat, Pyewacket, to cast a love spell on Shep. Shep is immediately enamored with Gillian and breaks up with Merle on the morning of their wedding. Gillian makes it so that author Sidney Redlitch (Ernie Kovacs) visits Shep in the hope that Shep will publish his next book, about witches in New York. When Gillian learns that her warlock brother, Nicky (Jack Lemmon), is collaborating with Sidney, she is worried that Shep will learn about her true nature and her spell on Shep. Since Gillian finds herself actually falling in love with Shep, something that will make her lose her powers, she must make a choice as to what she really wants.