Carl Donovan is Alex Sawyer's cellmate when he first arrived in Furnace. He was put away after killing his abusive step-father in a fit of anger.
Donovan is a sixteen year old teenage boy described as being tall and muscular. He has been described with having dark skin multiple times.
Donovan displays an air of indifference and toughness in Furnace to avoid being targeted by the various gangs. While inmates make room for him and respect his reputation, Donovan avoids causing trouble or picking fights with the gangs.
Around Alex and Zee, he is much kinder, more like an older brotherly figure who shows Alex around Furnace and teaches the rules of the prison. Having been through punishments like Solitary and seeing the punishments from acting out of place, Donovan often scolds Alex for breaking the rules and initially rejects the idea of escape. Donovan has a change of heart after seeing a mid-transformation Blacksuit Monty tear Kevin Arnold to pieces, and becomes willing to engage in Alex's plan.
In the beginning of Lockdown, Donovan swears that there are no friendships in Furnace and that he could not afford to get attached to anyone in the prison. However, later in the book, even though he entertains the thought of escaping with just Alex, he gained strong ties with the other boys and stays in loyalty.
Donovan's friend whom Donovan first starts mentoring when they first meet. Alex initially gets on Donovan's bad sides after picking fights and breaking rules during his first Bloodwatch. Despite this, the two eventually become closer as cellmates, and eventually as friends. After Donovan is taken, and in the beginning of Solitary, Donovan acts as a guardian angel to Alex as a hallucination (ironically enough, exactly what Donovan had first claimed he wouldn't become).
An inmate and mutual friend of Alex's that Donovan becomes friends with during the events of Lockdown. Zee also helps Alex and Donovan with their escape plan.