Once it was a farmhouse, a great Federal affair of brick and hand-hewn oak that majestically held a Pennsylvania knoll just west of Philadelphia. It was a very old house—any architecture major could tell that—for down beneath the basement was a chamber as dark as the grave. This had been a depot on the Underground Railroad, a hiding cellar for northbound slaves. The landholders, generation after generation, had given over their rolling soil and their Quaker time to corn and cows, and for a very long while there it would seem the clock stood still.
Then one day the ledger told the...