Shadow of the hangman

"1815. Peter and Paul Skillen are identical twins, fearless thief-takers who rival the Bow Street Runners. When they catch a notorious burglar, they claim a handsome reward and infuriate the Bow Street Runners, who believe they have a monopoly on policing in the capital. The Home Secretary, Viscount Sidmouth faces a crisis. During a massacre of American prisoners of war at Dartmoor, two escape and come to London in search of retribution. The Home Office has another problem --its cleaner has been abducted. Peter and Paul Skillen are hired to catch the fugitives and find the missing cleaner"--