Paddy was a young Irish boy, he has Halo figures and used to enjoy playing it. He hopes to become a good fighter one day and so looks up to Achilleus. He originally stayed with Just John and his squatters, but he sees an escape when Achilleus shows up. He begs Achilleus to train him as a fighter, in return for becoming his Caddy. This earns him the nickname of 'Paddy the Caddy'.
Achilleus treats Paddy like dirt to begin with, seeing him as a gullible slave, but by the end of The Fallen he realises how much he cares about the boy.
In The Fallen, they travel to the Promithios complex, where they find the twisted kids and other horrific sights. Paddy is scared out of his mind, and when they return he has violent nightmares of what could have happened had Achilleus not been there to help him. Keeping Paddy safe becomes a top priority for Achilleus and it is the reason that he chooses not to search for Ella with Ed, though he denies this.
In The End, Paddy gets killed and eaten by a group of sickos and Achilleus is heartbroken.