Charles Péguy (1873-1914), a French writer and mystic, was an atheist and a fervent socialist before converting to Catholicism. He prayed until the end of his life for the conversion of his wife, and died in battle during the WWI. A year later, his wife asked to be baptized.
In June 1912, after his son Pierre became seriously ill, Peguy made a vow to God to go on a pilgrimage to Chartres.
He wrote afterward to his friend Lotte: "I believed it to be serious. I made a pilgrimage to Chartres ... traveled 90 miles in three days. The bell tower of Chartres is visible 10 miles away on the plain ... As soon as I saw it, I was ecstatic. I felt nothing, neither my fatigue nor my feet. All my impurities fell away at once; I was a new man. I prayed for an hour in the cathedral on Saturday evening; I prayed for an hour on Sunday morning before Mass. I prayed as I had never prayed before, I was even able to pray for my enemies ... My child is saved, I offered all three of them to Our Lady. I can’t take care of everything myself ... My children are not baptized. It’s up to the Blessed Virgin to take care of it."
Taken from La Médaille Miraculeuse, issue #65