Tom Craig (John Wayne) is just a modest pharmacist in gold-rush-era California until he discovers saloon owner Britt Dawson (Albert Dekker) is getting rich by forcing the local ranchers to pay protection money. Not one to stand for injustice, Craig rallies the ranchers and attempts to overthrow Dawson's rule. To turn the mob against Craig, Dawson poisons one of Craig's patients and frames the pharmacist, but when illness breaks out, Craig is the only one who can help.