"I should probably mention something right now before this story goes any further: my name is Theodora Grumman, and I am a liar."

It's hard for Thea to write four truths a day in the notebook her mother gave her for the summer. Especially when her grandparents' house on the Jersey Shore is even more packed with family than usual, and her cousin Jocelyn wont leave her alone. Jocelyn just might be the world's neatest and nosiest seven-year-old, and she wants to know what's in Thea's notebook. But Thea won't tell anyone about the secret she has promised to keep--or how she lost her best friend (Truth #12), whose name was Gwen.

Now Thea has to babysit in the afternoons, and all Jocelyn wants to do is spy on people. Neither of them expect to see Aunt Ellen and Aunt Celia at the boardwalk in the middle of the day, or for their aunts to lie and insist they were at work. Could it be Thea's not the only one in the family keeping secrets this summer?