“Number One Fan” – A desperate young murder suspect, Emma Briggs, (guest star Alicia Lagano, “The Client List,”) takes hostages at gunpoint then mysteriously insists that she will only negotiate with one person: Richard Castle, on “Castle,” MONDAY, OCTOBER 14 (10:01-11:00 p.m., ET) on the ABC Television Network. (ABC/Richard Cartwright) NATHAN FILLION, ALICIA LAGANO