A mother duck hatches her eggs and, while most of her ducklings are normal, one is grey, too large, and too clumsy to fit in among the others. Though she tries to accept him, the entire barnyard realizes that he simply does not belong and after a period of harassment he leaves to fend for himself. He is sheltered by an old woman in her poor cottage, but her cat and her hen will not accept him and he is forced to set off once again on his own. He wanders for the entire summer and fall, for no one will take him in, and he nearly freezes to death in an icy pond. Though he is rescued by a human, he cannot live in captivity, and he returns to the wild.
By the end of winter, he is miraculously still alive. He comes to a pond in a park or garden, where beautiful white swans are swimming. He is drawn to their beauty, though he has no reason to think that they will treat him better than anyone else has. Still, he thinks, even if they kill him, he must approach them. To his surprise, the beautiful creatures welcome and accept him; gazing at his reflection, he sees that he too is a swan. The children declare that he is the most beautiful swan of them all, yet he is not proud, for a good heart is never proud. Because of all that he suffered he now appreciates his happiness so much more.