What is the main conflict in Bonhoeffer: Pastor, Martyr, Prophet, Spy by Eric Metaxas?

This biography of German theologian Dietrich Bonhoeffer, martyred by Adolf Hitler at the end of World War II, draws substantially on Bonhoeffer's own writings as it chronicles the development of his Christian faith and how a determination to live according to that faith led him into a conspiracy to kill Hitler. At the same time as it focuses on Bonhoeffer's determination to understand and live God's will, the narrative also explores themes related to the nature and value of loyalty, and the value of both friendship and family.