Elizabeth Wakefield and her best friend, Amy Sutton, have big plans for the holiday weekend, including a fabulous party, a family barbecue, and the chance to see a dreamy deejay broadcast live from the Sweet Valley Mall. But the weekend gets off to a surprising start when Amy's pen pal from San Francisco shows up unexpectedly. Samantha Williams seems every bit as nice as her letters until Amy introduces her to the Unicorns. Suddenly, the popular girls can't get enough of Sam and her stories, and Amy begins to feel left out. Why hasn't Sam ever told her about all those wonderful things she's done? Elizabeth and Jessica have a feeling she's making it all up. But will Elizabeth be able to stand by while her twin plans a coldhearted plot to uncover the truth?