I have been slowly working my way through Dietrich Bonhoeffer Works, Volume 16: Conspiracy and Imprisonment: 1940-1945
Here is a paragraph describing the arrest of Dietrich Bonhoeffer:
On April 5, 1943, less than a month after the failure of the March 1943 coup attempt, Dohnanyi and Bonhoeffer were arrested. Ironically, they were not arrested for their involvement in this coup attempt or for their role in the conspiracy efforts; Nazi officials were not yet aware of the full extent of their conspiratorial activity. What led to their arrest was currency irregularities in the Munich Military Intelligence Office Concerning Operation 7, the successful attempt to smuggle fourteen (0riginally it had been seven) “non-Aryans” into Switzerland. As Bonhoeffer wrote in this letter of August 26, 1942, Operation 7 lay very close to the hearts of the conspirators (13-14).