The ambiguity was real and has never been fully resolved. The historical record does not contain a detailed primary-source account of exactly what she was doing during the crossings, what she observed, what she reported, and how Union command understood her intelligence activities in relation to her medical mission. Walker’s own later accounts were advocacy documents as much as historical records, shaped by her interest in a specific telling of her story.
What is clear is that she was doing something in Confederate territory that the Confederacy found reason to arrest her for, that the Union found reason to exchange her for, and that her commanding officers found reason to recommend her for the Medal of Honor. The assessment of that something by the people closest to it, on both sides, was that it was significant.
## Castle Thunder in Context
Walker’s imprisonment at Castle Thunder from April to August 1864 is usually described in terms of its physical conditions — the overcrowding, the inadequate food and sanitation, the lasting physical damage documented in the pension record. These details are real and important, but Castle Thunder also had a specific character as an institution that provides context for what Walker experienced there.
Castle Thunder was opened in 1861 in a converted tobacco warehouse and warehousing complex on Cary Street in Richmond. It was intended for civilian prisoners, political prisoners, and alleged spies — the categories of prisoner that the standard prisoner-of-war exchange systems did not handle well. By the standards of Civil War prisons on both sides, it had a particularly harsh reputation, associated in contemporaneous accounts with arbitrary punishment and difficult conditions.