A summary on Harriet Tubman secret agent the book?

This book is about how Harriet Tubman escapes slavery and risks her own life to lead runaway slaves to freedom along the underground railroad. then she took a new role as a union spy! the outcome of a secret night raid deep into confederate territory depends on the accuracy of the intelligence she and other clack spies have gathered. success will mean freedom for hundreds of slaves. failure will mean death by hanging