David Koepp may not be a household name like his Oscar-nominated leading man, but he has carved out a darn nice career as a blockbuster screenwriter (''Jurassic Park,'' ''Mission: Impossible,'' ''Spider-Man'') and respectable thriller director (1999's ''Stir of Echoes''). With ''Secret,'' he takes another stab at the genre, adapting a Stephen King novella about an author (Johnny Depp) who retreats to a lakeside cabin where he's tormented by a mysterious kook (John Turturro). ''My mother always asks, 'A nice little comedy -- what would be so hard about that?''' says Koepp. To hear Depp talk about it, Mom's not going to be pleased this time, either: ''I read it and was like, yeah, great, it's classic Stephen King,'' he told EW. ''And then suddenly you go, 'Oh, s---! Are you kidding?' It makes this gigantic leap.'' Not that life on the Montreal set was all thrills and chills, thanks to the success of Depp's ''Pirates of the Caribbean.'' ''We hired an actor and got a movie star,'' says Koepp, who adds that Depp handled his exploding celebrity with ease. ''He just found it all kind of surprising and amusing and silly.''