from "Crime Pays: The Hollywood Gangster, 1930-1938" http://xroads.virginia.edu/~UG02/gangsters/scarface.html
Scarface - Plot Synopis
The plot centers on the rise and fall of Tony "Scarface" Camonte, whom the audience first see taking out Big Louie Costello, last of the old-style gangsters. Tony then becomes the right-hand man of new boss Johnny Lovo, strong-arming saloon keepers into buying Lovo's beer. Meanwhile, the women in Tony's life - Lovo's ice-cold moll, Poppy, and his young sister, Cesca. Tony catches Cesca kissing a suitor in the hall of their tenement home. Outraged, he throws the man out the door. Cesca is determined not to let her unnaturally protective brother boss her around, and we see her throwing a coin from her window to Tony's right-hand man, Guino.
Tony's ambitious exploits cross over into the territory of the Irish North Side gangs, led by O'Hara. After a corpse is dumped outside of Tony's headquarters, he takes revenge by having O'Hara assassinated. The Irish gangs fight back, using the new weapon of the streets - the machine gun. Entranced by the gun, Tony rushes out to take down his rivals. Scenes of gang warfare follow, with the cold-blooded murder of seven gangsters in a reenactment of Al Capone's real-life St. Valentine's Day Massacre. Tony is moving up in the gangster world - both Gaffney, the leader of the Irish gang, and his own ostensible boss Lovo live in fear of his wrath.
The audience sees Tony at a performance of Somerset Maugham's Rain. He's not so caught up in the performance, though, that he isn't able to leave at intermission for a hit - this time, on Gaffney. Afterwards, at the Paradise nightclub, Tony sits down with Lovo and Poppy. Poppy makes it clear that she is happy to see him - when the two men offer their lights for her smoke, Poppy chooses Tony's. Lovo, left alone as he watches his moll dance with Tony, plots revenge. Tony's own happiness is shattered when he sees Cesca, clad in a revealing sleeveless dress. In a rage, he wrenches her out of the hall and drags her back home.
When Tony steps out, a hail of bullets awaits. He jumps into his car and eludes his pursuers. Suspicious, Tony and Guino concoct a plan to determine whether Lovo was behind the attempt on his life. Lovo, shaky and obviously guilty, begs for his life before being shot down by Guino. Tony is now king of the gangsters.
Tony leaves for a month in Florida to celebrate his triumph. When he arrives home, he finds that Cesca has moved out. In a frenzy of jealousy, he tracks her down to her new apartment, where we see her happily playing the piano for Guino. Tony shoots down Guino while Cesca's horrified scream echoes across the soundtrack. Cesca screams at her brother, revealing that she had been married to Guino the day before. She reviles Tony, calling him a butcher. Tony staggers to his hideout, where Cesca tracks him down, gun in hand.
Suddenly, police sirens break into the silence. Instead of shooting her brother, Cesca runs into his arms, telling him that she's not afraid of going down with him. Gloriously happy at the prospect of a showdown with his sister at his side, Tony is drawing the steel shutters shut when Cesca is hit by a bullet. Tony carries the mortally wounded Cesca to a sofa, where he weeps over her, telling her that without her he will be completely alone. With her last words, Cesca accuses Tony of being afraid and calls for Guino.
A tear-gas grenade forces Tony out of his protected room and down a flight of stairs - where policemen await at the landing. The cops shoot Tony's gun out of his hand as he prepares to open fire. The defeated Tony pleads for his life, crying "Don't shoot....I don't got nobody....I'm all alone." The police attempt to take Tony into custody, but he runs frantically out the door, where he is cut down in a hail of bullets. The camera travels from Tony's body to a sign flashing "The World is Yours" above the tattered corpse.