While trying to uncover the truth about a long-buried history between Lucy Sable and Ryan Hudson, Nancy finds herself in the curious position of having to strike a deal with Horseshoe Bay’s newest and most suspect widower.

The gang resolves to find a way to speak with the only eyewitness to Lucy and Tiffany's murders -- Lucy herself. Nancy is faced with a truth that seems to validate her greatest fear.

After discovering a connection between the poison that killed Tiffany Hudson and a Horseshoe Bay cold case, Nancy and the Drew Crew risk their lives to bring a serial killer to justice.

While using a combination of forensic clues, skilled observation and relentless questioning of those who knew Lucy at the end of her life, Nancy unravels what happened the night Lucy died. While her detective work succeeds in some ways, it also reveals a devasting truth.