He is Charles Hatt's son and Sir Topham's grandson. He allies with Ryan to cause mischef for Sodor and take control of the North Western Railway. He is later revealed to be the son of Simon Johnson. After framing Phil Aardman for building a doomsday device and taking over his railway, Stephen found that Charles Hatt was in fact not his biological father, and thus the railway was not his inheritance as he had thought. Phil stated that he would press the most severe charges possible, but ultimately did not press the severe charges as anticipated. Stephen was taken to court and recieved five years in prison.
While in prison, he reads about his father's history about attacking Sodor. This led to him idolizing his father and wanting to finish what Simon could not. He hired two actors to pretend to idolize Robert Stewart and ask him to build a military base on Sodor. Around the same time, Mason, the sole surviving member of the Order of Cas-Ny-Hawin, was released from the sanitarium he has been sent to and began working with Stephen . He then hired a man to buy two diesels, 7101 and Diesel 10, from Lewis Packard. When Lewis refused, Stephen orchestrated Lewis’s death, as Lewis’s wife Jenny was more agreeable. The diesels were then forcibly given to Phil. 7101 was sent to the military base and renamed Bear, while Diesel 10 was used to help repair the Mid Sodor quarry, and also to keep the steam engines from interfering from his plans.
In 1968, when Stanley Aardman went missing, Phil and Robert’s search for him eventually led them to Phil’s surveilance bunker. Here, they were captured by Mason and Stephen, who had ambushed and killed Mr. Hugh, who was supposed to be watching the security footage. Stanley had already been kidnapped by them. Stephen then revealed that he was behind both the military base and Lewis’s death. He also revealed that Bear unknowingly had a bomb in his engine. Stephen remotely detonated the bomb, which started a fire that burned down the base. He then turned his attention to Stanley and said he was going to kill him to prevent him from taking over the railway after Phil retires. Stephen shot Stanley point-blank in the head. This infuriated Robert enough to break free of the ropes that he was tied up in. Robert tackled Stephen and began beating him until he was covered in blood. However, Robert failed to notice Mason coming behind him with a pistol. Robert turned around to see a gun to his head and was killed.
Stephen then allowed Mason to leave. Mason took a machine gun and carried out a massacre at Maron Park. Stephen, meanwhile, threw Phil to the ground and began stabbing him with a knife until he lost so much blood that he could barely move. When Michelle and Anne entered the bunker in hopes of finding Stanley, they were horrified. Stephen charged at Michelle and Anne with the knife, intent on killing them. However, Phil managed to reach his arm out far enough to trip Stephen. Stephen fell onto the blade of the knife, which impaled him through the chest and killed him.
- Season 3: Inheritance Parts 1, 2, 3, 4, 5, 6 and 7
- Season 4: Sins (death)