Mason was one of the five mercenaries hired by the SAS soldier Jake Hemple, in order to assist Jenny and Helen, in finding the kidnapped Cutter, Abby, and Connor. He is described as being young and thin, with brown hair. At the beginning of the book, he assisted Hemple in dealing with an Entelodon rampage, on Oxford Street. Later on, he travelled with the other mercenaries to Siberia, where he witnessed Jenkins die in a Troodon attack. (Extinction Event).