The story is about a pretty sophisticated girl named Caroline Waters who just turned 18. She has a 5-year-old little brother and her parents in her house. Her life was going as normal as possible until she got a letter through under the main door of her house and then, the mystery began. The words written in the letter astonish her a lot. She finds out a bunch of unknown things about some people which include her family members. Step by step, she is moving near to the exit door of this mystery and also to the sender of The Letter. But who is capable to do all these alone? Capucine Evans, Lilly Wilson and Jacob Williams, her three close friends, are going to give their hands to their friend. But nobody knows how it's gonna end.