In San Francisco in the Gold Rush days of the 1850s, a district attorney is prosecuting a long gang leader for murder. However, a powerful political boss is protecting the killer, and he gets off. Outraged citizens form a lynch mob, but before they can accomplish their task another murder is committed, and the culprit appears to be the brother of the District Attorney's fiancé. The D.A. believes the young man was framed for the murder to take the heat off of the gangster's acquittal, and sets out to find the real killer and who is behind him.