Zoe says that just before Tara's death, Tara had been scared that a professor there that she'd been sleeping with, Edward Fosca, would kill her. On the news, it's reported that a young woman ( Tara) has been murdered, who turns out to be a close schoolmate of Mariana's niece Zoe (whose own parents died in a car accident). Mariana is a young widow who is grieving her late husband Sebastian, who drowned a year ago. In Part I, the book flashes back to a few days prior. She is determined to find a way to prove it. The Prologue introduces Mariana, who is certain that a man named Edward Fosca has murdered two people. However, Mariana manages to fight Zoe off, and Zoe ends up arrested and taken to a psychiatric facility. The plan was to involve Mariana in an investigation into a series of murders (all committed by Zoe), frame Fosca and finally kill Mariana. After his accident, Zoe decided to continue with his plan of murdering Mariana (to get her fortune). Zoe had been lovers with Sebastian, who married Mariana for money. In the end, it's revealed that Zoe is the killer. Tara had been one of the Maidens and soon two more of the women are found dead.

Mariana gets drawn into investigating Fosca as well as the Maidens, a cult-like group of women who idolize Fosca. Zoe suspects Edward Fosca, a handsome and popular professor who Tara had been sleeping with. She goes to visit her niece Zoe at Cambridge after Zoe's friend Tara is found murdered. The one-paragraph version: Mariana is a young widow whose husband Sebastian died in a swimming accident last year.

The maidens alex michaelides