Biography
Robert Douglas was a Baltimore-area clergyman detained during the federal crackdown on Confederate sympathizers in Maryland and listed among the political prisoners held at Fort McHenry. (Recorded as The Reverend Robert Douglas)
Additional source for this Civil War detention: John A. Marshall, American Bastile (1869), printed pages 158-164, https://archive.org/details/americanbastile00marsgoog/page/n171/mode/2up. This is a partisan retrospective account; its judgments should be read as attributed claims.
Case
Fort McHenry