Henrietta worked with Toby on their old tramway in East Anglia. She became depressed when buses and lorries took over her work and when their line closed, due to the lack of passengers and freight, Toby could not bear to leave her behind. So Toby brought her with him to the North Western Railway. He mentioned to the Fat Controller that a stationmaster on his tramway wanted to use her as a hen house, but the Fat Controller agreed that "that would never do".
At first, Toby and Henrietta were teased by James for having shabby paint. However, Toby and Henrietta later received new coats of paint for their hard work and James stopped teasing them after he crashed into some tar wagons and spoiled his own paint. When Daisy was brought to Sodor, she insulted Annie, Clarabel and Henrietta when she found that she had to share a shed with them. Percy and Toby were forced to take them away and stay up half the night trying to soothe their hurt feelings. Later, she was used as the Fat Controller's private coach when the engines took a big trip to the Other Railway.
Henrietta is often used to carry quarry workers to and from Anopha Quarry. Once, some workers had to crowd on Henrietta's balcony. However this caused controversy with a Policeman, who informed the quarry manager of a by-law forbidding passengers to be carried on coaches' balconies. This problem was resolved when the Fat Controller restored an old coach named Victoria to help Toby and Henrietta. Together they formed "Toby's Vintage Train".
The villagers loaded her up with paint pots and presents to give to the engines as a token of gratitude for their hard work in the snow. During a snowstorm, Henrietta allowed Farmer McColl's sheep and newly-born lambs to warm up inside her cabin until the snow thawed. Sometime afterwards, Toby and Henrietta attended the Great Waterton tram parade, alongside Flora and her tram coach.
Henrietta helped Toby get over his fear of Knapford junction and Thomas was sent to pull her (unseen) when Samson accidentally took the express coaches by mistake, because Gordon had to take Annie and Clarabel.
She later advised Toby to go to the Steamworks to fix his wobbly sideplates and also told him to fill up with coal on his way to the scrapyard, which he did not. She later heard Paxton talking to Emily about Toby being scrapped and knew that it was nonsense. Emily took Henrietta to the scrapyard where they found Toby safe, but out of coal.
Henrietta is Toby's faithful coach, who likes to be full of passengers and take them on journeys. She does not like to be separated from Toby, although she rarely carries a full load of passengers. Henrietta is quite content with her life on the Island. Toby is attached to Henrietta and always takes her with him, as he says "she might be useful one day".
Henrietta is also seen motivating and encouraging Toby when he feels nervous about the capabilities of his work and performance.
Henrietta is based on a Wisbech and Upwell 4-wheel passenger coach. It is revealed in an annual that Henrietta has only one sister left, a bogied version of herself.
Henrietta is painted an orange brown with a black running board and red bufferbeams.