Zachariah and Rachel Wolff are siblings. Zachariah is Rachel’s parents' adopted son. As children, they were as close as two people could be. But when they crossed this forbidden line, there was no going back. As an adult, coping with Zach's estrangement from their father, Rachel is determined to invent a family history for her beloved. The novel cartwheels through Zach's imagined ancestry. All the while, their troubles are building to a new point of no return.