Widowed and in need of a job, Kate Warne convinces Allan Pinkerton that a female detective can go places and do things a male detective cannot. Once hired, Kate becomes skilled at lock picking and surveillance, but she is best in disguise--as a prostitute, rich matron, spinster, clerk, Southern belle--an expert liar, playing a role. She investigates burglaries, bank robberies, embezzlement, counterfeiting, blackmail, and murder. Eventually earning the respect of her fellow detectives, Kate comes up with an ingenious plan to protect President Lincoln from a Southern assassination plot. During the Civil War, she must fight against a formidable adversary--notorious Southern spy Mrs. Rose Greenhow.-- adapted from book review.