 Many literary scholars believe that Shakespeare's main source was an earlier play—now lost—known today as the "Ur-Hamlet".Possibly written by Thomas Kyd, the "Ur-Hamlet" would have been in performance by 1589 and was seemingly the first to include a ghost in the story.Using the few comments available from theatre-enthusiasts at the time, scholars have attempted to trace exactly where the "Ur-Hamlet" might have ended and the play popular today begins.