Young Meg Merlin, who hero-worships a dancer at her elite ballet school, is heartbroken when prima ballerina La Darina arrives to rival her idol. So Meg devises a plan. One little tug on a light switch while La Darina dances Swan Lake will ruin the performance. But Meg pulls the wrong switch -- the one that opens a stage trapdoor -- and sends the prima ballerina into a career-ending plunge to the floor below. Margaret O'Brien and Cyd Ch