The scowrers were worried about a pinkerton man, Birdy Edwards, because he was a part of the famous and prominent U.S detective company, Pinkerton, which is famous for tracking down a person without giving up or loosing hope.
No matter what happens, Pinkertons' will always track you down!
McMurdo's plan was to call Birdy Edwards to the lodge (since it was the area scowrers had most control over) and then everyone would take him down.