Seventy years before Purple Rose of Cairo, Woody Allen's film-inside-a-film, Buster Keaton got there first. Sherlock Jr., in which Keaton stars as well as directs, features a cinema projec­tionist who daydreams himself into the movies he shows. In the process he becomes subject to the plastic forces of time and space, which Keaton himself manipulated without peer. An endlessly recursive dynamic builds up, whereby one phantasmagoric world vanishes into anoth­er, is transformed and reappears. As the projec­tionist's favourite alter ego, Conan Doyle's immortal detective lends narrative intrigue, a wealth of gags, and infinite opportunities to sleuth out brilliant 'discoveries'.