Caroline Fremont Jones revels in her return to San Francisco, where a new city rises from the ruins of the 1906 earthquake. Even more rewarding is her business partnership and rekindled love with ex-spymaster Michael Archer Kossoff. But their private investigation agency is barely off the ground when Fremont's new friend, lovely but quirky Frances McFadden, becomes their first client—and it's a most troubling case.
The adventurous but skeptical Fremont, lured by Frances to a séance, sees her companion fall into a disturbing trance. Despite the opposition of her powerful, controlling husband, Frances is determined to develop her budding psychic ability. Soon she confides to Fremont that a restless spirit from San Francisco's legendary past has entrusted her with a mission.
But when one of the city's female mediums is murdered, and then another, Fremont's reservations turn to dread. Who has killed these women who wield their own power in the metaphysical world, and why? As Fremont's investigation takes her into the murky depths of spiritualism, she places not only herself, but also her dearest friends in mortal danger.