This gravestone commemorates a covenanter, John Hallime, who was executed by Captain Douglas in 1685 during the 'killing times'.
For more information and tour details St Cuthberts Graveyard check out Kirkcudbright History Societies website:
http://www.kirkcudbrighthistorysociety.org.uk/news/kirkcudbright-kirkyard-tours/
For more information on the Covenanters in Scotland check out BBC Scotland's website:
https://www.bbc.co.uk/scotland/history/covenanters/the_killing_times/
Theres also an entry on the Canmore website for the graveyard:
https://canmore.org.uk/site/64069/kirkcudbright-st-cuthberts-church-and-graveyard