The Sum of All Fears

So I could laugh off his fear of the inflatable robot and the Abominable Snowman in the Rudolph video. Ha ha. But last night, Chas was completely and utterly terrified by... the bathtub. It took quite a bit of doing, but Steph finally got him into the tub. Oh to be finished with the fear for the night after the bath.... About 2:30 a.m. I heard him crying in his bed. I tried to call him in to the "big bed" but nothing doing. I went to get him and he insisted that he wanted rocked in the rocking chair, not taken to the big bed. OK. I rocked him until he closed his eyes, then put him in his bed so I could get some sweatpants on. He freaked. By now his brother was awake and trying to get into the big bed. I helped him in, but Chas wanted to be in his own bed. I was really tired. So I stayed in the big bed. Within a few moments, Chas was screaming again, but allowed me to bring him into bed with the rest of us -- where he kept my neck in a death grip. We even woke up to blow away the bad dreams. I thought we were cool, with his head right up against mine and I fell asleep. Suddenly, directly in my ear, he lets out the loudest, most high-pitched scream I have ever heard. T'was not a good night.

What has made this boy so fearful? More to the point, what's it gonna take for me to get a good night's sleep???