Build a movie plot around this: Why does Harmonica help Frank kill his men? Because of flashback
Answer:
In the desert Southwest of America during the waning days of the Old West, three gunmen (Jack Elam, Woody Strode, Al Mulock) approach an isolated train depot; two are wearing duster overcoats. The men take over the station and settle in to wait for the train. When the train finally comes, a nameless harmonica-playing stranger (Charles Bronson) gets off and asks for someone named Frank. They tell him Frank sent them in his place. In the ensuing showdown, all four men go down. Only the man with the harmonica gets up again.The soundtrack to the opening scene is a creative orchestration of ordinary sounds in the style of John Cage. Composer Ennio Morricone uses dripping water, the clicking of a telegraph, a buzzing fly, and over all the persistent, annoying squeak of a windmill-powered pump to build tension, punctuate visual jokes, and emphasize the tedium of waiting for the train. The scant dialog allows the soundtrack to consume much more of our attention than a score usually does.On a remote farm called Sweetwater, Brett McBain (Frank Wolff) and his children are preparing an outdoor wedding feast. McBain tells his son Patrick to drive into town to pick up his new mother, who is arriving by train from New Orleans. Suddenly shots ring out from the desert, and McBain's daughter Maureen, son Patrick, and McBain himself are slain. The youngest McBain, Timmy, runs out of the house to find that his entire family has been destroyed. He watches in terrified silence as a group of five gunmen in duster overcoats emerge from the scrub brush. When one of the men calls their leader Frank by name, asking what to do with the child, Frank (Henry Fonda) draws his pistol and slowly takes aim at the last remaining witness. With a self-satisfied grin, he pulls the trigger.In the town of Flagstone, McBain's bride Jill (Claudia Cardinale) steps down from the train to find that no one is there to meet her. Giving up hope, she steps through the train station into the bustling new town still being built. She hires a carriage to drive...