Ryan realizes what Judith is up to almost as soon as she walks through the door to interview for a position that she’s far too qualified for. He recognizes the nosey reporter from pictures Lacey had shown him, but he also knows that kicking her out will only make her think he has something to hide. He’s sure that Lacey’s death was nothing more than a tragic accident, and he assumes the best way to prove that to Judith is to let her stay at The Puppet Factory and do a little investigating of her own. The fact that he is attracted to her has nothing to do with it.
The only flaw with Ryan’s plan is that Lacey’s death was no accident. And the closer Ryan gets to Judith the closer the killer gets to her.