When Boone Dixon and his sister Heather arrive on the bus headed to Camp Hither, Boone ends up sitting next to a nervous boy named Roddy McDonald. Boone at first mishears his name and thinks he's called Ronald McDonald. Roddy is afraid to go to camp because he had heard stories from other kids. About how the camp is really called Camp Slither, how the camp is infested with snakes, and how the kids have to swim the lake, which is home to a giant snake named Serpo. He's head that the campers who head to Camp Slither never return. Boone tries to calm down Roddy, but after Heather rattles her bracelet, he panics. When the kids arrive at camp, things don't go any better for Roddy. The kids are all sprayed with some strange orange liquid called Sun-Glo sunscreen. At the campfire that night, he panics when he hears snakes, only for it to be the sound of crickets. Not only that, but the camp engages in an event called Cabin Wars, which also bothers him. When it comes time for the kids to swim the lake, Roddy panics yet again and decides not to swim. When Boone returns, Roddy has disappeared. The counselors claim that Roddy left the camp, but his belongings are still in his cabin.
Boone, Heather and two other boys named Sid and Kelly try to find out what's going on. It eventually is revealed that Dr. Crawler and the other counselors were human scientists that after an experiment gone wrong have turned themselves into snakes. The Sun-Glo they sprayed on the kids was snake DNA, in an attempt to turn them into snakes as well. It's there where the kids learn that Roddy is being turned into a king snake. Before Dr. Crawler can turn the other kids into snakes, Boone grabs Roddy and has him attack Dr. Crawler. Dr. Crawler tries to defend, but bites himself, killing himself instantly. The other snake counselors make a run for it. Roddy then turns back to normal as the effects of the experiment only lasted five minutes.
Roddy had huge black framed eyeglasses, and has white-blond hair (that's cut short), he also had very pale blue eyes. When Roddy is at 95% snake completion he is mentioned to flick his long forked tongue but is still mostly human. When Roddy is finally transformed into a snake, he comes out as a long yellow belly king snake, which helps him later in the book.
Roddy has a "wimpy" personality, mostly because of his big fear of snakes. Also, this may be because one of the kids at school told him a legend of the camp named Serpo (a giant snake that supposedly lives at the bottom of the camp's lake). When he is in snake form, Roddy is aggressive toward the other snakes at the laboratory, ultimately dodging an attack from Dr. Crawler, causing Dr. Crawler to inject himself with venom. Roddy does appear to have an interest in Manga as he brings one to camp with him. He is also superstitious and carries a good luck charm.