Siblings Matthew and Elizabeth Janssen, eighteen and seventeen, together with their parents, take a long family vacation in Cape Cod, since Matthew leaves for college in the fall. Curious, the two teenagers start exploring and discover a secret room in the cottage they're renting for the summer. In this room, they find a dusty old grandfather clock with a letter hidden inside. This mysterious letter alleges that the clock is actually a time travel device. The letter writer, John, claims that, in 1927, he went back in time to save his cousin Alice, who was murdered in 1907, and whose ghost is doomed to forever flee down the beach, trying to escape her murderer—but to no avail. However, something happened, and John got stuck in 1907. He begs whoever finds the letter to figure out what went wrong with the clock and fix it, returning him to his own time of 1927. Is it all a hoax, or could it possibly be true? And once Matthew and Elizabeth figure out what went wrong, fix it, and return John to his own time, will they be able to resist temptation to try it on their own? After all, the clock's been fixed, so what could possibly go wrong?