Terence was helping build a barn on the day Victoria was sent back to Thomas' Branch Line. After swerving for a boulder by the Hackenbeck tunnel his trailer fell down the cutting and balanced dangerously on a tree.
As in the Railway Series, Terence went to rescue Thomas when he got stuck in the snow. He later helped Mrs. Kyndley, when her house was snowed up, and looked after her house when she went with the engines to a Christmas Party. In the second season, he befriended Duck while Thomas was at the works, and attended the Christmas Party at Tidmouth.
In the third series, he helped Trevor with the planting of new trees in the forest after a storm and assured Henry that the forest would look better than ever before. He also got trapped near a level crossing when Mavis got stuck and blocked the road. When Bertie got stuck in the mud at the Vicar of Wellsworth's party, Terence used strong ropes to pull him out. Later, when villagers were stranded by snow, Terence helped them by ploughing the snow away. In the fourth season, he was seen working at a farm near where Sir Handel had an accident.
In the fifth season, he warned James about the damage that trees can do, and reminded Percy that Mrs. Kyndley's daughter was to get married. He was also seen working at Boulder Quarry.
In the sixth season, he helped clear away fallen rock on the line which had derailed Thomas, and almost Toby. He was later seen ploughing in a field, when Duncan lost his whistle trying to surprise him.
In the seventh season, he helped clear away a tree that had fallen on the line, and pulled Elizabeth out of the snow.
In The Great Discovery, when Thomas went missing, Terence helped with the search for him, and once Thomas was found, Terence informed Harvey of the news.
In the twenty-first season, Terence takes a shortcut over a frozen lake while collecting Christmas trees for the holiday market, but in the process the ice begins to break.
Terence is an assertive, orange tractor with caterpillar tracks. The engines find these very unusual, but Terence is very capable of proving that he does not need rails and that his tracks allow him to go practically anywhere. He takes any teasing in the name of fun and is happy to get on with his job, usually partaking in agricultural work. Terence never hesitates to assist in emergencies or sticky situations, road or rail, due to his helpful, forgiving nature. His tracks are particularly invaluable in harsh winter conditions when snow can affect transport across the Island. He may be slow, but he is versatile, adaptable, and helpful. He can usually be found transporting agricultural produce or cheerily ploughing fields beside Thomas's branch line.
Terence is based on a 1934 vintage Caterpillar Model Seventy - the largest, and last, design of petrol-powered tractors in Caterpillar's range.
Terence is painted orange with grey caterpillars and a black engine and exhaust pipe.
He was only ever shown with two face masks in the television series, both of which were smiling, though he was illustrated with a wider variety of expressions in the Railway Series, annuals, and magazine stories.