Since being saved from scrap, Trevor has been living in the vicarage orchard and is enjoying his time there, especially as Edward stops everyday to talk to him. However, Trevor sometimes finds himself with not enough work to do. One day, Edward stops to talk to Trevor as usual and the traction engine was feeling downbeat about not being busy or having company all the time. He is especially sad that he does not get to spend time with children very often.
Edward has some good news for Trevor; the Fat Controller has asked that Trevor be sent to the site of the new harbour to help out with the work. Edward has been sent to pick up Trevor and carry him to the yard to meet with Thomas, who will take him to the harbour. Trevor instantly perks up, looking forward to a trip to the seaside where he will get to work and hopefully meet some children.
Thomas, who is carrying items needed for construction work, is introduced to Trevor by Edward in the yard. Thomas is wary of the unusual-looking newcomer and asks what a traction engine is. Trevor explains that he is an engine who runs on roads instead of rails before politely asking to be taken to the harbour. Thomas, who is still confused, agrees nonetheless.
After Trevor's truck is coupled onto Thomas' train, the two set off for the harbour. On the way, Trevor explains his usefulness to Thomas, but the tank engine still cannot fathom how an engine can ruff off rails. Trevor tells Thomas he will understand later.
At the harbour, Thomas arrives to find chaos. Several trucks have been derailed which are blocking the line and stone slabs are now littering the area. Thomas' driver tells Thomas and Trevor that the equipment Thomas is carrying is essential, so Trevor must go to work taking it around the mess. Trevor, who enjoys this kind of work, is happy to do the job as soon as possible.
While Thomas moves the trucks, Trevor carries the contruction equipment to where it is needed with chains. Later, Thomas brings Annie and Clarabel to the harbour to meet him. Thomas has been left very impressed with Trevor after seeing him work so hard and finally understands just how useful a traction engine can truly be. Both Annie and Clarabel are carrying children, who Trevor is more than happy to give rides to. This is easily his favourite part of the day and Annie and Clarabel remark to each other how kind and gentle Trevor is and how he reminds them of Thomas.
Thomas and Trevor are both very sorry when the day is over and Trevor has to return to the orchard. Taking him to the junction, Thomas tries to cheer up an upset Trevor by telling him that there is now plenty of work for him at the vicarage and that he could be needed at the harbour again some day as well as promising to visit whenever he can. Trevor is left feeling much better by the news.
That evening, Trevor remembers all that had happened that day. He made a new frined in Thomas, he got to work at the harbour, but best of all, he got to spend time with children. With those thoughts very much in his mind, Trevor falls happily to sleep in the shed at the bottom of the orchard.
- Trevor whistles at the beginning without a driver.