Aethelthryth was then married to Ecgfrith of Northumbria in 660. Ecgfrith was a younger son of King Oswiu of Northumbria and his wife Enfleda. Shortly after Ecgfrith became king, Aethelthryth asked her husband if she could become a nun. She was encouraged by Bishop Wilfrid to remain . This caused friction between Ecgfrith and Bishop Wilfrid. One story tells that Ecgfrith first agreed that she should continue to remain a virgin but in about 672 he wished to have an heir. He tried to bribe Wilfrid to convince the queen to give him an heir. This failed and the king tried to take his queen from her convent. She fled back to Ely with two nuns and managed to evade capture. The legend says that she escaped due to the miraculous rising of the tide. Another version of the legend stated that she stopped on the journey at 'Stow' and hid under an ash tree which suddenly came from her staff after she planted it in the ground. This came to be known as 'St Aethelthryth 's Stow', when a church was built to commemorate this event. Stow Minster contains a stained glass window that portrays the legend. Ecgfrith later married Eormenburg and expelled Wilfrid from his kingdom in 678. According to the "Anglo-Saxon Chronicle", Aethelthryth founded a double monastery at Ely in 673, which was later destroyed in the Danish invasion of 870. She lived at St. Ely for the remainder of her life in pious devotion. She died of the plague. There is a hymn that was written in her honor.