The Underground is a six-book spin-off series that follows the lives of six Russian fighters who were introduced in The Fight Club series. This series will be best read in order as there is an escalation of events in each story that lead to the eventual answers concerning how and why these six fighters' lives are so intertwined. Each book follows a different fighter and the woman who captures his heart.

This book is a re-release of a previously published book. No additions or changes have been made to the story.