It’s the typical story: Kid in bed, not only scared of the dark, but also scared of the doll that he thinks is moving. The only difference here is that it’s got a twist with the kid actually being a child of clowns. I don’t think the kid should really be scared of the doll then, but more of what he’s predestined to be, what with being born a clown and all.
Soon, however, he becomes scared of much more than that when he sees what he believes to be his mother going through a transformation from clown to a normal person. And that’s basically it. Surprising, huh?