David Moreno Mingote

Professor Freeman is an important English scientist that is investigating a method to treat cancer. His daughter is killed in the swimming pool of a hotel in Beirut. The case is confidential so that the mission is entrusted to the Special Agent Mikel Brown.

Shenandoah (Steffen) works his way into a band of highwaymen led by Rojo (Armando Calvo). His initiation consists of hunting down and killing a member of the gang who has 12 bullets while he is only given 2 bullets. When the bandits attempt to rob a wealthy rancher, whom Shenandoah knows, he warns him. The outlaws begin to suspect they were betrayed and commence to rough Shenandoah up. Shenandoah then reveals his true reason for joining the gang; one of them killed his wife and he is there for retribution.

Ranch owner MacGregor has seven sons and oldest Gregor leads his brothers to Las Mesas, a small town where they want to sell horses. They get into trouble with local people who are related with evil Santillana. After getting imprisoned and losing their horses they decide to go after Santillana's gang.

A master criminal is pursued by inspector Milton