Henrietta is Toby's faithful coach, based on the Wisbech and Upwell Tramway non-articulated GER four-wheeled coach. She worked with Toby on their old railway, and when that line closed Toby could not bear to leave her behind. The stationmaster had wanted to turn her into a henhouse, but the Fat Controller agreed that "that would never do." The two are inseparable, and whenever they are apart they worry about each other.
Henrietta was the only named character not to be illustrated with a face in The Railway Series until book 41 of the series, Thomas and Victoria. In this book, Henrietta is depicted with a small rectangular face where a window on the end doors would be. It is the same colour as her cabin, like the other coaches.
Henrietta carries passengers and is used to bring quarry workers to and from work. In "The Fat Controller's Engines" (The Eight Famous Engines), she is used as the Fat Controller's private coach when the locomotives take a trip to The Other Railway.