 He was a friend of her brother-in-law, another of the future leaders of the 1916 Easter Rising, Thomas MacDonagh, who was married to Grace's sister Muriel.Her growing interest in the Roman Catholic religion led to the deepening of Gifford and Plunkett's relationship as she began to discuss Catholic mystical ideas with him – he was from an arch-Catholic family, his father a Papal count.Plunkett proposed to her in 1915; Grace accepted and took formal instruction in Catholic doctrine.