This paranormal romance, the second installment in the Three Sisters Island trilogy, is set on a small, fictional island off the coast of Massachusetts with a centuries-old legacy of magic. In a prologue set in September 1699, the sister witch known as Earth stands on a storm-swept beach and sends a killing curse at the man who murdered her sister Air during the Salem witch trials. Despite warnings from her second sister, Fire, that using power to harm will corrupt her gift and rebound threefold, Earth sacrifices her soul for vengeance.
In January 2002, Deputy Ripley Todd, the island's athletic, thirty-year-old deputy sheriff, is trying to find a place of her own so that her brother, Zack Todd, the island's sheriff, and his new wife, Nell Channing Todd, can have their privacy. Ripley possesses magical abilities she has deliberately suppressed for over a decade and shares a deep rift with Mia Devlin, the island's bookstore proprietor and a practicing witch. When Ripley approaches Mia about renting a small yellow cottage, Mia informs her it has just been leased to Dr. MacAllister Booke, a paranormal researcher from New York. That night, Ripley dreams of Earth wielding dark magic on the beach and watches as a lance of fire kills Earth's husband: the threefold return of her curse.
Mac arrives the next day, an earnest scholar who has spent nearly twelve years studying the occult worldwide. He fills the cottage with paranormal equipment, and when Ripley helps him carry in boxes, their handshake causes his energy sensor to spike. That night, he sees a ghostly apparition of the original Earth sister on the beach, weeping and glowing faintly. Mac maneuvers Ripley into cooperation by challenging her to a swimming race: If he wins, she gives him one hour of her time. He beats her by two strokes. During the resulting interview, her protective fury causes her to accidentally burn his wrist with an uncontrolled burst of power. Ashamed, she heals the burns with a spoken charm, using magic openly in his presence for the first time. When Mac drives her home, he kisses her on the porch, and she walks into the door afterward, dazed.
Ripley confides in Nell that her powers have been resurfacing since the previous Halloween, when she used magic to help save Nell from her violent ex-husband, Evan Remington, now confined to a mental facility. Mac builds relationships across the island, paying Lulu, Mia's surrogate mother and bookstore clerk, for interviews, and discovering the Halloween circle site in the forest. Mia invites Mac to dinner and recounts how she, Nell, and Ripley cast the circle through will alone to protect Nell from Remington. She tells Mac they are not meant to be lovers, a conclusion he has already reached.
Ripley, jealous about the dinner, confronts Mac unfairly, then recognizes her mistake and apologizes. They grow closer. Meanwhile, Jonathan Q. Harding, a ruthless magazine reporter from Los Angeles, visits Remington at his facility. Remington is heavily sedated but becomes animated when Harding mentions "Helen," Nell's former name. Harding begins tracking Nell's cross-country flight from her abusive marriage.
Mac explores the island's south point and discovers a cave near the empty Logan house containing a Gaelic love inscription. When Mia finds Mac and Ripley there, she is devastated: It was the site of her first lovemaking with Sam Logan, the man who broke her heart years earlier. In a rare moment of vulnerability, Mia tells Ripley she misses her. After seeking counsel from Lulu, Ripley goes to Mac's cottage and initiates their first night together. She realizes she has fallen in love with him, and the shock causes every machine in the cottage to spike simultaneously.
Mac reveals that his many-times-great-grandmother, Constance, lived on Three Sisters in 1758 and was a descendant of one of the original sister witches, making him a distant blood relative. Constance's journal describes a dark, ageless evil and contains a protective charm in Gaelic intended for her descendants. Mac tells Ripley first because she matters to him most. Mia accepts the connection warmly, calling him "cousin," and gives him a family pendant from their shared line.
On Valentine's Day, Harding visits Remington again. When Remington grips Harding's hand, something dark passes between them. Harding arrives on the island plagued by violent dreams. Mac runs paranormal tests on Nell and Ripley; under hypnosis, the spirit of Earth briefly takes over Ripley's body, warning of a dark force: "He brings death. He craves it" (268). Ripley has a prophetic nightmare in which she wields a silver sword and kills a man whose face shifts between three identities, but the dark magic rebounds, killing Mac with lightning.
Ripley uses astral projection to visit Remington's facility. Despite being in a coma, Remington senses her and attacks her spiritually, leaving burns on her chest. Mia tends to the wounds. Ripley then goes to Mac's cottage intending to break up with him, hoping to force him off the island. Mac sees through her. When she blurts out that she loves him, he responds in kind and refuses to leave. She tells him Todds mate for life, and he has to marry her. He reveals he has put in an offer on the Logan house, and they exchange tokens: her grandmother's ring for a silver talisman he bought years ago in Ireland.
The dark force drives Harding into the woods, where he attacks the protective circle. He stumbles into the café, and through him, Remington's voice speaks to Nell, calling her "Helen," but Nell stands firm. The group gathers for confrontation. Mac hypnotizes Ripley with Mia and Nell as her protective circle and plants the charm from Constance's journal in Ripley's subconscious. The spirit of Earth warns each woman of what lies ahead. The dark force attacks, hurling furniture and shattering glass. Mac brings Ripley back to consciousness, but she sees blood on his face from flying glass. Horrified that her power has shed his blood, she runs into the storm.
On the beach, Harding, fully possessed, confronts Ripley. The entity conjures a sword of black lightning and strikes Lucy, the family's dog, who falls motionless. Enraged, Ripley conjures her own silver sword and fights the entity in a fierce duel, her rage growing darker with each blow. She beats the entity down and raises the sword for the killing blow, repeating the original Earth sister's fatal mistake. Mac's voice reaches her through the storm, and she sees her loved ones outside her barrier of fire.
Ripley stops the blade an inch from Harding's throat. She recites the protective charm from her subconscious and cuts her own palm on the blade, letting her blood, already mingled with Mac's, fall on Harding. The five of them form a ring and perform a casting-out ritual, expelling the dark entity into the sea. Mia reveals Lucy is alive: The sword strike was an illusion designed to provoke Ripley into killing in rage.
In the aftermath, Ripley tells Mia and Nell about a vision she saw when she stopped the sword: the three of them in a circle, and everything being okay. She also saw Mia alone on her cliffs, surrounded by darkness, and warns that the strongest challenge will come for Mia. She saw Nell holding a baby as well. Walking home with Mac through the moonlit forest, Ripley tells him that feeling his love is even better than the power of magic. They plan to marry and live in the house by the sea.