On the Little House on the Prairie TV show, Mary Ingalls and her husband on the show, Adam Kendall had a baby, Adam Charles Holbrook Kendall Jr.
In the two hour episode May We Make Them Proud, there was a fire at the Harriet Oleson School for the Blind, that was accidentally started by Albert and Clay smoking a pipe in the school’s basement. Alice Garvey attempted to save baby Adam from the fire, but she became trapped in the flames and both she and Adam Jr. died in the fire.
After Adam Jr.’s death, Mary fell into a deep depression. When the school is rebuilt, it is renamed The Alice Garvey and Adam Kendall Jr. School for the Blind.
The TV version of Mary Ingalls, and the real Mary Ingalls the character was originally based on are quite different. The real life Mary Ingalls did not have a baby, nor did she get married.