A good author holds absolute power over the light-switch in your mind. The writer teases you, maybe even throws the switch for a second and then throws it back off again several times over the course of the story. He drops hints that are only misleading enough to keep you guessing until the brink of sheer madness. He draws it out until the last possible effective second and then BAM!, that light-switch slams on and all you can say is

oooooooooooohhhhh