Number One Fan A desperate young murder suspect, Emma Briggs, takes hostages at gunpoint then mysteriously insists that she will only negotiate with one person: Richard Castle. Details Casts Title Number One Fan Genres Drama Crime Release Date 2013-10-14 Episode Runtime 00 Hours 45 Minutes Season Number 6 Episode Number 4 Production Companies Beacon Pictures, Experimental Pictures, ABC Studios, The Barry Schindel Company, MilMar Pictures Nathan Fillion Richard Castle Stana Katic Kate Beckett Molly C. Quinn Alexis Castle Jon Huertas Javier Esposito Seamus Dever Kevin Ryan Susan Sullivan Martha Rodgers Tamala Jones Lanie Parish Penny Johnson Jerald Victoria Gates