I believe that if you do a forum search on Subject, and simply type in "Grace" you will likely find several threads on this song. It concerns Joseph Mary Plunkett and Grace Gifford. Plunkett was sentenced to die by firing squad for his role in the Rising. He fought even though he was a very sickly person ("I had to leave my own sick bed..."). He was engaged to marry his Grace and she was brought to him in the chapel of Kilmainem. They were surrounded by British soldiers and were not allowed to touch one another, nor even kiss. They were married by the Priest and the next morning he was taken out and shot.