The man drowns in the ocean so Bulstrode rescues him and takes him back to the docks so he can dry off. Later, a cargo car hits Bulstrode as he goes across the drawbridge. When he looks, it's just the man Bulstrode rescued earlier. The agent secretly confesses to Bulstrode about his career and asks him to vow to keep it secret. But it soon turns into a rumor, causing Bulstrode to be mocked by any engine that puffed past him.
It's not really certain if the man is actually the secret agent, but in the episode, at Elsbridge station, Sir Topham Hatt practices a surprise entrance for his wife's birthday. The agent is in front of the door, so when Sir Topham Hatt opens the door, he accidentally injures the agent, so he sues and replaces Sir Topham Hatt as the railway controller. But isn't very nice, so the engines decide to go on strike and think of how to get him off the railway. Thomas hears that he likes coffee so Salty tells Thomas to get rid of the coffee beans on Sodor so that the Agent will leave. The next day, the Agent was shocked and angry when he realized that his coffees were gone and decided to bring Sir Topham Hatt back and leaves the railway. (however this might have been someone else)
The Agent stands by the Control Tower at the airport. Henry comes by with The Flying Kipper. He mistakes him for a signalman. He asks him which way he should go. The agent gets baffled so Henry explains what the signalman does. So the agent quickly decides to send Henry on the right track, and Henry obeys. But Henry accidentally crashes into the Cookie Factory Cars.
The Agent drives the Crosby Station Cargo Truck with Edward's new side rods. He just skids to let the cargo out and drives away without talking to anyone. Fearless Freddie gets suspicious and follows the truck. The agent drives onto the track as they go up the spiral mountain. Once he reaches the top, he stop and thinks he heard noises. But then is trapped by Fearless Freddie and Skarloey. The bridge breaks and the cargo truck falls to the ground right in front of Madge, but the agent jumps out and lands by the suspension bridge. He survives and isn't injured much, but then goes back to his original destination.
Duck mistakes him for the Railway Inspector, but when he asks where he can apply to become a ticket collector and says he's not the Railway Inspector, he rants about previous events in Bulstrode and the Fisherman, The Kipper Caper and Edward Breaks Down. However, this goes unheard by Duck.
The Secret Agent goes undercover at Knapford Station after Gordon had recently heard from the Railway Inspector that he lost his privileges of pulling the Express. This passenger is seen waiting to hop in the coaches for some mystery and this goes unknown by the engines.
Because of the Railway Inspector's terrible review, the passengers refuse to ride on the engines' daily trains. So Sir Topham Hatt brings Bertie and Bulgy to take the passengers for the engines, the Secret Agent is one of the passengers who is taken by Bulgy but the engines hardly recognize him.
In "Harvey's Happy Accident", the man returns to Sodor as a passenger, once again going unnoticed by the engines.
He continues his latest visit on Sodor in "The Maron Station Makeover" as one of the passengers who is complaining about Maron Station as well as repeating that his shoelace is untied.
As controller at one point, he completely disliked the engines and preferred to not stay as the controller of the railway. However when he left after an incident, the Secret Agent still make visits to the railway uninvited and it is unknown what the rest of his personality is like.
- Season 8: Bulstrode and the Fisherman and The New Controller
- Season 9: The Kipper Caper
- Season 10: Edward Breaks Down
- Season 11: The Great Western Way
- Season 12: The Importance of Being Billy, Gordon's Last Hurrah (does not speak) and Bulgy Takes the High Road
- Season 15: The Maron Station Makeover, Ice Ice Daisy (cameo)
- Secret Agent has been noticed once by all members of the Steam Team, that episode is The New Controller.
- He took control of the North Western Railway once but was immediately replaced back by Sir Topham Hatt hearing the engines disliked the man.
- After some episodes, engines don't know this man's fate.
- In Season 12, Secret Agent has been in some episodes but unnoticed by engines: in The Importance of Being Billy, he was pretending to be one of Rosie's passengers who had lost their baggage, in Gordon's Last Hurrah, he pretends to be just a regular male passenger at Knapford Station waiting to go on Gordon's express train and in Bulgy Takes the High Road, pretends to be a passenger who wants to ride a bus instead of an engine.
- He made an appearance in Oliver's Eleven still unnoticed.