Fergus is going to work at the quarry and he tells Thomas that he is going to work hard to make the Fat Controller proud of him. Thomas warns Fergus to watch out for Bill and Ben who like to play tricks. Fergus is determined not to let the mischievous twins bother him and sets off to the quarry as quickly as he can.
When Fergus arrives, Mavis explains that the trucks are in a bit of a mess. Fergus does not mind and tells Bill and Ben to "come along" before cheerfully setting to work. Bill and Ben do not like being told what to do. They vow to have Fergus in a spin before the day's out. They are sure he will not want to work at the quarry after that. The twins start to bang their trucks making rocks fall out onto the line. Fergus orders the twins to "do it right", but Ben rudely tells Fergus to mind his own business.
Later that day, the men start blasting at the quarry, so the engines have to stop work. The quarrymaster orders Bill and Ben to collect a new rock crusher. As they leave the quarry they hear Fergus calling out "do it right" to them. When the twins get to the harbour, they are still complaining about Fergus. They decide that the next time Fergus tells them to "do it right", they are going to do it wrong.
On the way back to the quarry, the rock crusher is so heavy that it makes the rails shake. This gives the twins an idea and they decide to pretend to push the crusher right into the rockface; they are sure this will annoy Fergus.
At the quarry, Bill and Ben clatter in and loudly make their way towards the rockface with the heavy crusher. Fergus is alarmed and orders Bill and Ben to keep away, but the twins take no notice. Rocks begin to tumble down and Fergus rushes forwards. He bumps Bill and Ben out of harms way just in time. Fergus' driver jumps clear, but Fergus is left covered in rocks.
It takes a long time to free Fergus, but thanks to Bill and Ben's hardwork, he is soon uncovered. The twins are very ashamed and apologetic. Fergus is glad to hear that the twins have learned their lesson and Ben promises to "do it right" next time.