Ian Rider is Alex's uncle who had custody of him after his parents died. Ian was supposedly a banker, but when he suddenly is killed by a "car accident", Alex finds out that he was actually an MI6 secret agent who was killed in action.
Jack Starbright is an American housekeeper for Ian and Alex. She lives with them and cleans in return for money. She is Alex's only hope left when Ian dies. Alan Blunt threatens to send her back to America if Alex doesn't work for them.
Alan Blunt is the Chief Executive of the Special Operations Division of MI6. He assumed the role of "bank chairman" when Ian Rider was killed. He gave Alex his missions along with Mrs. Jones.
Mrs. Jones is the Head of Operations at MI6. She gives all the agents their missions. She and Alan Blunt blackmailed Alex into working for them.
Wolf was one of the men that Alex trained with. He constantly harassed Alex, but Alex did him a huge favor by pushing him out of a plane when they were skydiving. Alex saved Wolf's career.
Herod Sayle is the villain of the story. He is building Stormbreaker computers for all British schools. However, he is secretly putting devices in the computers that will release a lethal disease. He attempts to kill Alex and fails. Yassen Gregorovich kills Sayle in the end.
Yassen Gregorovich is a Russian paid assassin who killed both Ian Rider and Herod Sayle. He was working to assemble the Stormbreakers.
Mr. Grin is Herod Sayle's...