Monty's father died a month before he was born, leaving him to be raised only by his mother. He was born as the older twin to a girl named Nan. However, Monty's mother couldn't afford to raise both children, so Nan was raised by her uncle, Leo, in Pennsylvania. Meanwhile, Monty was raised in California.
As a zoologist, Monty's mother was required to travel to Borneo for a year, leaving Monty with Uncle Leo and Nan; Monty thinks the girl is his cousin — but he found out the truth during his stay. Monty started seeing an evil version of himself running around. As Monty learned, Uncle Leo created a clone of himself that turned out to be evil. This clone then created evil clones of Monty.
Monty was mistaken for a clone and was hauled away. He escaped and returned to Nan, trying to prove his authenticity. But he failed and was hauled away to South America with the clones.
Monty is embarrassed about his looks, as well as his full name, Montgomery. He claims to hate adventure. He proves to be quick witted when he tricks his clones into fighting with each other.
Monty is described as skinny with red hair and a big nose.
- The cover art depicts Monty's hair as light brown — possibly even blond, despite it being red in the book.