Lady is a beautiful girl and the mysterous magical steam engine in Thomas & the Magic Railroad.
Lady was chased and wrecked by Diesel 10 long ago and was brought to safety by Burnett Stone. She was brought back to life with the help of Burnett's granddaughter Lily after being stored at Muffle Mountain for years, and helped Thomas defeat Diesel 10.
Later in Calling All Engines!, she and Rusty appeared in a dream to Thomas. Lady told Thomas how to resolve the problems Sodor was facing.