The Cheyenne are convinced that newly-arrived settlers have been killing the buffalo they traditionally depend on. When the Native Americans surround the 20th Cavalry's fort, Lucky Luke realises that someone who bears a grudge against Colonel McStraggle has provided them with firearms. Worse, the tr...

The Cheyenne are convinced that newly-arrived settlers have been killing the buffalo they traditionally depend on. When the Native Americans surround the 20th Cavalry's fort, Lucky Luke realises that someone who bears a grudge against Colonel McStraggle has provided them with firearms. Worse, the traitor also knows the layout of the fort.