E. Skinner "Skinny" Norris was a rival of the sleuths, and has made several attempts to defeat them. As a legal resident of another state that had a lower age restriction, than California, for driving, he could possess a driving license, unlike The Three Investigators.
Right from when the sleuths started their firm, he had proved to be a hindrance for them. When Bob Andrews was searching information about the Terror Castle in the library, he had left one of the firm's business cards with "Terror Castle" written behind. Skinny saw this and quickly came to the Terror Castle to hinder their investigations.
While hunting for the treasure of Dingo Towne, Skinny once attempted to run the trio down with his car. Jupiter and Pete managed to get off of the road in time, but Bob's bicycle was nicked by Skinny's car. Later, he set the trio adrift in an old houseboat that ended up going over a dam, putting their lives at great risk by his actions. It was only the quick thinking of Peter Crenshaw that saves their lives.
Later in the books he even traps the three sleuths in a room and plots to steal a ranch from one of their friends named Diego Alvaro, and as punishment for being quite diabolical, he was sent to a military school by his father.