When Evan Ross stays for a few days at his Great Aunt Kathryn's, Trigger travels with him. Trigger tries to attack Kathryn's cat, Sarabeth, after Sarabeth jumps on Evan, and Kathryn makes Trigger stay outside in a pen.
After meeting Andy, Evan finds Monster Blood in a toy store. They play with the Monster Blood outside, and a little falls by Trigger. Trigger eats the Monster Blood and begins to grow in size, causing chaos. Later, after the Monster Blood is defeated, Trigger returns to his normal size.
Finally, he returns home with Evan.
In this book, Trigger does not have much protagonism. He only appears at the end of the story with little Evan climbing over him to ask for help from his father.
Trigger returns in Monster Blood IV, accompanying Evan back to Kermit's house.
Trigger is a Cocker Spaniel. He has a brown coat.
Although disobedient, Trigger is incredibly loyal to Evan. He chases away the Beymer twins, who were bullying Evan, and he pursues Sarabeth just as she is about to kill Evan.
- Classic Goosebumps
- Monster Blood