It might be 1893 and the modern world may in full-swing, but cowboy Gustav "Old Red" Amlingmeyer is an old-fashioned kind of guy: he prefers a long trail ride even when a train could get him where he's going in one-tenth the time. His brother Otto ("Big Red"), on the other hand, wouldn't mind climbing down from his horse and onto a train once in a while if it'll give his saddle-sore rear end a rest. So when it's Old Red who insists they sign on to protect the luxurious Pacific Express, despite a generations-old Amlingmeyer family distrust of the farm-stealin', cattle-killin', money-grubbin' railroads, Big Red is flummoxed. But Old Red, tired of the cowpoke life, wants to take a stab at professional 'detectifying' just like his hero, Sherlock Holmes and guard jobs for the railroad are the only ones on offer. So it is that Big Red and Old Red find themselves trapped on a thousand tons of steam-driven steel, summiting the Sierras en route to San Francisco with a crafty gang of outlaws somewhere around the next bend, a baggage car jam-packed with deadly secrets, and a vicious killer hidden somewhere amongst the colorful passengers.