Early one summer morning in 1850, as Penny McGinty leans over a cookstove in the sweltering Philadelphia kitchen, a knock from a slender fist upon the back door of the tall, narrow house interrupts the hum of insects hovering in the yard's overgrown garden. At first, neither Penny, nor the wealthy family for whom she cooks, nor the niece who spends her hours reading in the upstairs drawing room, nor even the man tending his horse in the stable...