Martin Dunn is an Orange who enjoys using his abilities to hurt others. Upon his arrival at Thurmond, apparently aware and in control of his Psionic abilities, he 'convinced' another boy, a Green, to trade places with him. Martin was classified as Green.
When Cate stops at a gas station to meet up with her other "agent", Ruby slips into the other agent's mind and sees that he has killed two innocent children in an alleyway. She quietly slips away to hide in the store and escapes with Suzume. Martin is unaware of this, as he is still with Cate and the other agent, Rob.
Soon enough, they realize what is happening and chase after Ruby and Zu, who are now with Liam and Chubs in their Dodge Caravan, Black Betty. Rob has given Martin a gun, and he fires at Black Betty, causing it to swerve on the road. However, Liam uses his telekinetic Blue abilities to make a tree fall over and collapse on Rob's car. They are then presumed dead, but at the end of the book, Ruby pushes her panic button and Cate arrives shortly with Martin, too. Ruby wakes up in a safe house, with Cate sitting beside her. Martin walks into the room, and attempts to flirt with Ruby, but she, having learned to control her abilities by Clancy, wipes Martin's memories and tells him he should leave if he doesn't know what he's doing.
Never Fade (mention)
Ruby is told by Vida that Martin tried to touch her. This adds evidence to the fact that Martin only uses his abilities to benefit himself.
Martin is described as being a psychopath who likes to use his abilities to manipulate and "break" people's minds.
Ruby first meets Martin when escaping from Thurmond, and describes him as "round all over", with drooped cheeks, and a uniform that seemed to be a size too small. Ruby estimates he must have been around her age, one year younger, probably. He's rather short, one or two inches shorter than her (making him around five-foot-four or five-foot-three). He has floppy brown hair and dark brown eyes, and, upon closer inspection, Ruby notices the freckles on his face and "the way his eyebrows seemed to merge into one".
Brother - Nurse Dunn - mentioned in Sparks Rise