San Francisco astrologer Julia Bonatti's life is turned upside down when she becomes the target of the city's newest cult leader, Reverend Roy of the Prophet's Tabernacle. Driven out of her apartment in the midst of a disastrous Mercury retrograde period, she takes shelter with a client who's caring for two elderly aunts. One aunt appears stricken with dementia and the other has fallen under the spell of the Reverend Roy. To add to the confusion, a young man claiming to be a long lost nephew arrives. The longer he stays, the more dangerous things become. Is the young man truly a member of the family? Can astrology confirm that? Julia's not sure, but one thing she does know is that Mercury wasn't merely the messenger of the gods—he was a trickster and a liar as well.
Julia is an Astrologer who has private clients and also works for a newspaper answering astrological questions, she is stunned when she starts to receive vicious emails and phone calls, her apartment is targeted (leading to possible eviction!) and she finds out that others in the alternative therapy sector are being got at as well, she tries staying at her Gran's house (whilst she is away) only to discover that the boiler needs replacing which means no heat and no cooking facilities! So she ends up going to stays at one of her private clients houses - but the night she arrives one of the elderly sisters up and leaves to join the very group that has been making her life a misery. Julia needs to work with Mercury to help the two sisters and get her own life back.