Mary Edgar was born on 27 December 1907 in London, England, UK, daughter of Jenny (Howard) and George Edgar, an author. She was educated privately. On 6 March 1934, she married Rudolph F. Mussi, they had , Max, and one daughter, Susan Jane.
She was a past chairwoman of Society of Women Writers and Journalists. She started writing contemporary romance novels as Mary Howard in 1930, later she used the penname of Josephine Edgar to sign her gothic historical romances. She was the recipient of the Romantic Novelists' Association award in 1960, 1979, 1980, and Elinor Glyn award in 1961.
Mary Mussi passed away on 02 March 1991.
