After Thomas acted cheeky to Gordon one day, Gordon decided to pay him out by pulling him away before he had been uncoupled from his coaches. Thomas was pulled across Sodor at high speed and afterwards resolved to never tease Gordon again, but this brief excursion beyond his boundaries seemed to give him a desire to see more of the world and be part of it.
Thomas was given charge of Henry's morning train after he fell ill, but forgot to be coupled and only stopped when a signalman told him that he had no train. Thomas' real first chance at pulling a train came when Edward offered to shunt coaches while Thomas took a goods train for him to Wellsworth, but the trucks got up to their tricks and pushed him down Gordon's Hill; Thomas narrowly avoided a collision with the buffers.
After this incident, Thomas was permanently transferred to Wellsworth to learn the ways of the goods yards. After James came rushing through one day and crashed into a field, Thomas came to his aid and the Fat Controller, satisfied with Thomas' work, gave him charge of a branch line and two coaches named Annie and Clarabel.
Thomas was asked by the Fat Controller to run the main line with Edward while the big engines went on strike.
Henry finally got his revenge on Thomas by beating him to the junction, with the help of his new Welsh coal. Thomas was not cross, but instead was impressed by Henry's new-found power.
Thomas teased Gordon relentlessly about his incident with the ditch. He later went to an abandoned lead mine for some trucks and foolishly ignored a danger sign, causing him to fall into a mine tunnel. Gordon pulled him out and the two formed an alliance.
Thomas later asked the Fat Controller if Gordon could be forgiven and was chosen to shunt coaches for the other engines. He was personally thanked by Queen Elizabeth II.
As Thomas was busy, he asked Percy to take the children home from Sunday School.
Thomas warned Percy not to stray past the board at the harbour, citing his experience of falling down the mine as a warning.
Thomas later attended a meeting with the other engines, learning that he and the others were going to England. While teaching his temporary replacement, Jinty, how to run his branch line, he boasted about his famous race and crashed into some buffers, denting his front end badly. He was repaired in time and breathlessly arrived at Knapford just before the others left for England.
Thomas had a collision with the Ffarquhar stationmaster's house and was sent to be repaired. One of the major differences in Thomas' body upon his return was his valence, which was now flat instead of curving down, as it previously did.
Thomas befriended Stepney during his visit to Sodor. Stepney worked on his branch line during his stay.
It is said that Thomas' and Edward's branch lines are important, but their track and bridges are not strong enough as those on the main line.
Thomas teased Percy about his ghost train, but was later spooked when Percy, covered in lime, attempted to gain entry into the Ffarquhar sheds.
Thomas helps the police when he sees the thieves, who stole some valuables from the stationmaster. Also, after being cheeky to Gordon, Thomas was given the task of pulling the express along with Duck and Percy while Gordon and Henry were ill.
Thomas and Percy began a quarrel after Thomas became covered in coal dust, which became more serious as time went on. Finally, Thomas apologised after Percy helped him after he punctured his water tank and the two became friends again.
Thomas was sent to Edward's Branch Line whilst the bridges on his own line were under repair.
Thomas was invited to a railway show in York. The trip was shaky, with Thomas colliding with a crossing gate and later being booked for parking after the lorry he was traveling on parked illegally. Matters were compounded after Thomas frightened a small child while stopping for a bag carelessly thrown onto the line, but Thomas made up for his misdemeanours by saving Green Arrow from a dip in a river and was rewarded by being made an honorary member of the National Railway Museum and was given a commemorative plaque. For some reason, Thomas does not bear this plaque anywhere visible on his body after his return in the next book, where he is seen with it in front of his funnel.
Thomas arrives home from York in the last story and is greeted with a celebration.
Thomas befriends Wilbert upon his arrival on the branch line.
Thomas derails after running over track weakened by rabbit burrows.
Thomas spotted an old coach called Victoria who was run down and unused and suggested that she be mended to help Toby. After an overhaul at the Works, she became part of "Toby's Vintage Train".
Thomas helped to rescue an injured swan from a bridge parapet and later corrected Percy when he thought that the Thin Clergyman was bust, as in broken. He then attended the unveiling of the bust of the Thin Clergyman with the other engines at Tidmouth.