Twinkle enjoys wading in the brook near her home, and watching the fishes swimming in a pool. One day she finds an unusual little mud turtle, with red and yellow streaks on its shell. She takes the turtle home and keeps it as a pet. She is surprised to find that the turtle can talk, though only on one day a week, on Saturdays.
The turtle tells Twinkle a remarkable tale: he is a fairy prince — Prince Melga, son of the fairy queen Flutterlight — under an enchantment. He begs Twinkle's help to disenchant himself, so he can then fight a "corrugated giant." Twinkle can hardly resist his plea.
On the next Saturday, Twinkle takes the turtle in her hands. A sudden strong wind assaults her, forcing her to cover her eyes; when it stops, she is standing on the side of a mountain, overlooking a beautiful valley. The turtle instructs her to wipe her eyes with a leaf from the maita plant; afterward, she can see the gorgeous fairy palaces that fill the valley, built of silver, crystal, and mother-of-pearl, with filigree-work of gold and streets of jewels. She can also see the looming, grim, gray castle of the corrugated giant. Twinkle is fearful, but agrees to follow the turtle's guidance.
They sneak through the iron fence around the castle; the fence is a magic barrier against fairies, which is why the turtle needs a human's help. Smoke from the chimney shows that the giant is preparing his dinner. Twinkle and turtle enter the kitchen and confront the giant; he is twice the size of a man but ten times the bulk. He has no bones, so that his flesh sags in bumps and layers around him, accordion-like. The giant tells Twinkle he will keep her as his slave, or throw her to his seventeen-headed dog. He orders her to tend the fire; and Twinkle takes her chance to drop the turtle into the kettle of boiling water.
From a burst of steam, a handsome fairy prince emerges; the kettle has turned into his shield, and the long spoon is now his sword. Prince Melga kills the giant, stabbing him until he is dead. Prince and girl leave the castle, which dissolves behind them. Twinkle is welcomed as a heroine by the fairies, including the beautiful Queen Flutterlight. She is rewarded with a golden medallion that has a turtle embossed on one side. She is sent home the way she came. Her mother tells her that her turtle has escaped; Twinkle keeps her adventure a secret.
For the Prince's name, Melga, compare Prince Melra in Baum's story "The Witchcraft of Mary-Marie."