Complex sentence: After Chaplin learns that Purviance is really a woman, he kisses her while on the set; at this point, a male stagehand enters and, thinking that Chaplin has kissed a man, starts acting in an overtly effeminate way until Chaplin kicks him.
Split into simpler sentences: After Chaplin learns that Purviance is really a woman, he kisses her while on the set. A male stagehand sees this and thinking that Chaplin has kissed a man, starts acting in an overtly effeminate way until Chaplin kicks him.