In 1561 the 18-year-old Mary returned to a Scotland in the grip of the Reformation, as Protestant leaders had taken control of the Scottish parliament and abolished the authority of the pope.
Mary returned to Scotland in the month of May in 1561. 
mnli hypothesis: Mary returned to Scotland in the month of May in 1561.  premise: In 1561 the 18-year-old Mary returned to a Scotland in the grip of the Reformation, as Protestant leaders had taken control of the Scottish parliament and abolished the authority of the pope.