Murdoch is one of Sodor's largest and strongest engines.
Murdoch was brought to relieve the engines of their heavy workloads. He was big and strong, so the other engines were eager to learn more about him. Murdoch, however, disliked the noise of their chatter and got cross with Salty and Harvey when they inquired about his past exploits. The next day, Murdoch finally had a chance to pull a train through the quiet countryside, but his journey was interrupted by a flock of sheep. Murdoch had to wait with the noisy sheep until Toby could bring the farmer to lead them away. That night, Murdoch found Salty's and Harvey's company a relief. Murdoch was happy but shy about being decorated for the May Day festivities.
Murdoch is a mighty, powerful engine with ten drive wheels. He is one of the largest engines working on Sodor and was brought to the Island to help with the heavy workload and pull heavy goods trains across the Main Line. Murdoch is as shy as he is strong, as he is actually a gentle giant. He can often be found seeking peace and quiet, away from the bustle of the yards and the Docks. He enjoys long hauls through the countryside and, although he can get short of patience and a little annoyed if he does not get some alone time, he can be quite a reserved engine. Although he can be an independent worker, Murdoch is often content to join in, help, and offer advice where he deems it worthy, but, despite being hard to miss due his defining strength and size, he will not jump to put himself at the centre of attention.
Murdoch is a BR Standard Class 9F used for fast and heavy goods trains. The class was the last of the BR Standards, and the final steam engine class built by British Railways, with the last one, Evening Star, built in March 1960. Evening Star and eight other 9Fs are preserved. One 9F, Black Prince holds the record for hauling the heaviest steam-hauled train in Great Britain, at 2,198 tons.
Murdoch is painted orange with green and red lining. He has smoke deflectors, on which he wears red nameplates with gold lettering.
- In the UK narration of the twelfth season, Murdoch gains a Scottish accent.
- According to early concept designs of the Season 7 characters, Murdoch was originally going to be a BR Standard Class 7. Also, after his 9F class was decided on, he was originally going to be maroon red with chrome yellow linings, according to Robert Gauld-Galliers' original art work. Because Arthur was already going to be maroon with yellow linings, Murdoch's livery was changed to orange with green and red linings so that the two engines' colour schemes would not clash with each other.
- In his concept art, he seems to have a double chimney, which were fitted on 9Fs built from 1958 onwards.
- Murdoch shares the same whistle sound with Arthur, which itself is a LMS whistle stock sound effect.
- The Motor Road and Rail system previously spelt Murdoch's name incorrectly as Murdock.