To describe briefly, Mary was married three times:
The Murder of David Rizzio by John Opie (1761-1807)/Guildhall Art Gallery and Wikimedia Commons
Mary escaped the next year and fled to England in hopes that her dear cousin, Queen Elizabeth (whom she never met and who was also her son’s godmother) would help her regain the Scottish throne. Elizabeth's parents were King Henry VIII and Anne Boleyn.
Elizabeth believed Mary had designs of her own on Elizabeth’s throne (which most sources confirm) and kept her locked up in various places for 19 years.