Writing suspense/thrillers means becoming an expert on what frightens people. And let's face it: it's the unknown that scares us more than anything we can see with our own eyes.
It's the shadowy figure in Vicki's bathroom that moves in a disjointed, grotesque way... And isn't there when she turns on the light. (Vicki's Key)
It's not knowing when the bad guys are going to show up once the trap has been set - and not really knowing whether the trap will work. (Secrets of a Dangerous Woman)
Or finding out that the cameras installed in your home weren't put there by an alarm company - and not knowing what the viewers on the other end might have seen. (The Pendulum Files)
It could be arriving on deserted beaches in the dark of night after a hurricane devastated the island, knowing the killer is there, feeling his eyes on your back. (The Tempest Murders)
Or it could be something that seems to be completely innocent, like Detective Ryan O'Clery finding a pacifier on his office desk - and realizing the killer was in his little girl's room at home and also managed to get into his police department office. (The White Devil of Dublin, due out this fall)
What frightens you?