The Imaginarium of Doctor Parnassus, the movie Heath Ledger was working on when he died of an accidental prescription drug overdose, receives a gala screening at Roy Thomson Hall at 6:30 p.m. In attendance on the red carpet will be director Terry Gilliam and stars Christopher Plummer and Colin Farrell, who along with Johnny Depp and Jude Law stepped in to play different facets of Ledger’s character after his death.