The San Francisco Scheme: The Klondike Detective, Book 2 (Unabridged‪)‬

The Klondike Detective 2 continues the story of John Caldwell. He decided to take leave from the Northwest Mounted Police in Dawson City in 1902 to visit his family. Nearby, in Kingston Penitentiary, Cedric Barton and Robert McGill escape. These were men that John helped to convict, so he follows them to San Francisco. 

There, he becomes a Pinkerton's agent and then a double agent employed by Lila McGill, who is Robert McGill's mother, since the McGill gang is now at war with the Barton Tong. Another fellow working for Lila McGill is a treasury agent following Barton and his import of weapons, ladies, and cocaine. 

They follow the trail to Shanghai where John is recruited by the municipal police and then finds a double who looks like someone who works for Barton Tong. Naturally, John impersonates the fellow after hiding him. The adventure and mystery continue in this second book.