When Becca Thompson and Benjy Connor enter the sixth grade, they unfortunately end up with Mr. Blankenship as their teacher. Mr. Blankenship is a skinny balding man who fills his classroom with cages of snakes. Not only does he enjoy snakes, but he even appears to acts like one, hissing over a mouse that gets lost during a feeding session. Becca and Benjy sneak into the school one night to free all the mice that Mr. Blankenship has been using to feed his snakes. However, they soon see Mr. Blankenship shed his human skin and is actually a giant snake himself. The two kids make a run for it. The next day at school, they promise to feed Mr. Blankenship mice as long as he doesn't hurt them.
Becca and Benjy, along with their class, are at a nature center to learn about the food chain. To demonstrate, Mr. Blankenship feeds a mouse to a snake, which bothers Becca and Benjy. Later on, Becca finds a bunny with a lizard's face. They eventually discover that Mr. Blankenship has been experimenting on animals and himself to create the ultimate predator. He then transforms into a giant snake. Becca manages to defeat Mr. Blankenship by throwing a formula on him that turns him into a fly. The next day, the kids enter the bus to return home, thinking they no longer have to worry about Mr. Blankenship, but the now fly Mr. Blankenship follows them, saying that they're wrong.
The story version of Mr. Blankenship is described as a skinny, balding man who wears a long turtleneck sweater with a snakeskin pattern.