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 coat of paints for their hard work, and James stopped teasing them after he crashed into some tar wagons and spoilt 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 Sir Topham Hatt restored an old coach named, Victoria, to help Toby and Henrietta. Together they formed "Toby's Vintage Train".
In the television series, the villagers loaded her up with paint pots and presents to give to the engines as token of gratitude for their hard work in the snow. During a snowstorm, Henrietta allowed Farmer McColl's sheep and newly-born lambs warm inside her cabin until the snow thawed.
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 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.
In the Railway Series, Henrietta is painted brown with red bufferbeams. In the television series, she is painted an orange brown with a black running board and red bufferbeams.
- Despite not having a visible face until the eighteenth season, she had the ability to talk in the first and second seasons.
- Henrietta has appeared in every single season of the television series.
- "It's not fair, it's not fair at all! Just look at all those buses, full of passengers, and I've got none. I remember the day I use to be full of passengers, and have nine trucks rattle behind me! But now there only three or four..."
- Henrietta, Toby and the Stout Gentleman, Toby the Tram Engine.
- Toby had wanted to take Henrietta, but the Fat Controller had said, "No!"...He wondered if Henrietta was lonely. Percy had promised to look after her; but Toby couldn't help worrying. "Percy doesn't understand her like I do," he said.
- Toby and the Fat Controller, Double Header, The Eight Famous Engines.