In ice hockey, no one is tougher than the "goon". Those players have one mission: to protect the star players at any price. Exploring the violent world of hockey fights, Academy Award winner Alex Gibney ("Taxi to the Dark Side") looks at the world of the NHL enforcers and specifically the career of Chris "Knuckles" Nilan who helped the Montreal Canadiens win the Stanley Cup.

Archival footage and personal testimonials present an intimate portrait of the life and career and death of NHL tough guy Bob Probert.