Shelley Mizer is the daughter of Stan Mizer, the crackpot scientist who invented a water-fueled automobile.
Though she kept the papers of her father in the basement, she seemed to have a mixed opinion of the man. Apparently, he could be a difficult man to deal with some eccentricities.
When Byers and Frohike went to see her, she was unhappy to see Frohike again. He had made a bit of a scene trying to get at her father's papers. They managed to convince her to look through Stan Mizer's work this time. When they found a lead, she accompanied them on the quest to find the water fueled car.
The Lone Gunmen found the car they sought but Shelley Mizer convinced them not to reveal it to the public. She claimed that the repercussions of a car powered by water would not lead to a society with less problems but one with more problems. Vast numbers of cars would be made as the world consumed more resources not less. It would also not eliminate the need for oil as many parts of cars are made of oil byproducts and the water fueled engine still used oil for lubrication. It seemed that this was the conclusion that her father had come to but he didn't have the heart to destroy his invention. The Lone Gunmen, Yves Adele Harlow, and Jimmy Bond were convinced to keep the car secret.