Follow crime fiction’s toughest hero from San Francisco to the Mexican frontier in the third installment of the Collected Case Files of the Continental Op   The Continental Op is short, fat, and aging—but don’t let his appearance deceive you. Handy with a gun, and always willing to take a roundhouse to the chin, the Op is the toughest sleuth San Francisco has ever seen. And when a rich Englishwoman hires him to find her estranged husband, the Op thinks he’s in for an easy job. But the husband is an addict last seen in Tijuana, and finding him will take the hardboiled detective past the border and into a hellhole called the Golden Horseshoe.   Before Nick Charles or Sam Spade, Dashiell Hammett made his mark with the adventures of the Continental Op, whose particular brand of justice defined the legendary Black Mask style. In “The Golden Horseshoe,” “The House in Turk Street,” and “The Girl with the Silver Eyes,” the Op follows his cases from civility to temptation and back again.