Winthrop is a rich and snobby resident of Kepler. He is in an unspecified relationship with Muffy and works in hospital administration at St. Francis Hospital. His first appearance is when riding the funicular with Muffy, and Aubrey accidentally sets him on fire.
Winthrop is secretly part of a mysterious organization he refers to as the "Shadow Brethren", who communicate with each other in Latin and have been poaching endangered animals in the woods of Kepler for at least as long as Duck was in the forest service. Both him and Muffy express an eagerness to hunt the "greatest game of all," man.