Fox resembles an obese, red-faced man in a policeman's uniform. He speaks with an Irish accent, but his speech mannerisms are noticeably artificial and odd-sounding, like a caricature of a colorful, jolly Irishman rather than a real person. He habitually gets around by bicycle.
In 1916, Fox introduced Dear to Myles de Selby and escorted them on their venture into a God-Machine facility near Skerries, Ireland. Inside the facility, Fox revealed his biomechanical nature: he used needles embedded in his hand to transform de Selby into something like a clockwork servitor as punishment for stealing from the God-Machine. However, he then gave a clockwork brain to Dear and escorted him back to his home, allowing Dear to complete Mary.
Fox was the one who told Mary that Dear had abandoned her and moved to London. It is also implied that he is the angel who kept her sedated until 2012. When Jon Dear called 999 to report that Mary had broken into his house, Fox responded and stole Mary's letters, the only proof that she'd been stalking him. On August 13, when Stephen brought Jon and Mary to the production facility, Fox met the trio and deactivated Stephen. Mary willingly gave her key to Fox, who removed her clockwork brain and gave it to Jon, telling him to do whatever he wanted with it.