The Three Sisters is an Italian literary fairy tale written by Giambattista Basile in his 1634 work, the Pentamerone.
A woman had three daughters; the two older were very unlucky but the youngest, Nella, was very fortunate. A prince married her and hid her from his wicked mother, visiting her in secret. She could throw a powder in a fire, and he would come to her on a crystal road. Her sisters discovered this and broke the road, so that the prince was injured when he was coming to her.
He was dying. His father proclaimed that whoever cured him would marry him, if female, or have half the kingdom, if male.
Nella heard of it and set out. Hiding in a tree, she overheard an ogre tell his wife about the illness, and how only the fat from their bodies could cure the prince. She climbed down and presented herself at their door as a beggar. The ogre, greedy of her flesh, persuaded his wife to let her stay. When they slept, Nella killed them and took their fat. She brought it to the king and cured the prince. He said he could not marry her because he was married already; Nella asked if he wanted to be married to the person responsible, and the prince blamed her sisters. Nella revealed herself as his wife. Her sisters were thrown in an oven.