Herluin de Conteville suffered from a skin ailment for which he could find no cure.
"One night, while he was sleeping, the Virgin Mary appeared to him holding a branch with a white flower, a lily. She asked him if he wished to be cured. When he said yes, she told him: Go to a place called Grestain. Not far from a spring, you will find a chapel dedicated to me which has fallen into ruins. Restore the chapel and provide a priest to serve at the altar. Then you will be cured."
Soon after, through another dream, Our Lady ordered him to establish, in the same place, a convent of monks "to pray God night and day."
This is how Herluin, cured of his disease, founded the Grestain Abbey in 1050.