SALON presents a mini-whodunit. The first reader to guess the murderer's identity and the motive wins a $25 gift certificate from Borders Books and Music.

By DAVID TALBOT

The train that pulled out of L.A.' s Union Station on that shirtsleeve-warm evening in March 1933 was lit up with tinsel and 100-watt GE bulbs. But it was even more dazzling inside the passenger cars, which were filled with the brightest stars in the Warner Bros. galaxy: Bette Davis, Jimmy Cagney, Humphrey Bogart, George Raft, Busby Berkeley' s girls, and of course Tom Mix and his horse.

The glittering troupe was bound for Washington D.C. at the invitation of President-elect Franklin Delano Roosevelt, for Warner was the only studio to back FDR during the ' 32 campaign. Roosevelt wanted to add some Tinsel Town glamour to his inauguration festivities, the first such Hollywood-Washington alliance in political history. And the stars? Well, they did what Jack Warner told them to. And what he told each one of them as they boarded the train emblazoned with the WB and GE logos was to behave themselves. " You' re the distinguished ambassadors from the Warner Bros. studio," he reminded them, with the kind of scolding look in his eye that said it even more bluntly: You screw up and embarrass me and you' ll never work in this town again.