If you consult the Oracle Google about James McParland, you will find this wiki passage:
Reports of McParland's success against the Molly Maguires came to the attention of Sir Arthur Conan Doyle, author of the Sherlock Holmes detective novels. Conan Doyle wrote McParland into The Valley of Fear, creating an encounter between the fictional Sherlock Holmes, and a character whose history loosely recalled McParland's experiences with the Molly Maguires.
Conan Doyle had met William Pinkerton on an ocean voyage, where the writer became fascinated by the "singular and terrible narrative" of the Molly Maguires. Later, however, "William Pinkerton's and Arthur Conan Doyle's friendship ended over the rendition of some Pinkerton exploits in fictional form..."
The Valley of Fear is one of my favorite Conan Doyle stories, even though Holmes is not at the center of the tale.