Sixteen-year-old Gwen, the newest and final member of the secret time-traveling Circle of Twelve, searches through history for the other time-travelers, aided by friend Lesley, James the ghost, Xemerius the gargoyle demon, and Gideon, the Diamond, whose fate seems bound with hers.

In 1766, a boy, Billy Marvel, is shipwrecked, rescued, and goes on to found a brilliant family of actors that flourishes in London until 1900--and nearly a century later, Joseph Jervis, runs away from home, seeking refuge with his uncle in London, and is captivated by the Marvel house, with its portraits and ghostly presences.

Sixteen-year-old Gwyneth discovers that she, rather than her well-prepared cousin, carries a time-travel gene, and soon she is journeying with Gideon, who shares the gift, through historical London trying to discover whom they can trust.

Since learning she is the Ruby, the final member of the time-traveling Circle of Twelve, nothing has gone right for Gwen and she holds suspicions about both Count Saint-German and Gideon, but as she uncovers the Circle's secrets she finally learns her own destiny.