Oberon and Titania, king and queen of the fairies, both want a young Indian boy to be part of their entourage. Titania wants the child, who is half mortal, half fairy, because she promised his dead mother, her friend, that she would raise and care for the child. Oberon wants the child so that Titania won't lavish so much attention on it. As Puck puts it:
And jealous Oberon would have the child
Knight of his train, to trace the forests wild.
But she perforce withholds the lovèd boy,
Crowns him with flowers, and makes him all her joy
Matters come to an impasse. Oberon thinks Titania should obey him because he is her husband. She believes she should honor her promise to her friend. Their quarrel affects the weather:
Contagious fogs, which falling in the land
Have every pelting river made so proud
That they have overborne their continents.
The ox hath therefore stretched his yoke in vain,
The ploughman lost his sweat, and the green corn
Hath rotted ere his youth attained a beard.
To gain the child, Oberon is willing to play a trick on a Titania, putting a love potion in her eyes so that she falls in love with the first creature she sees, which happens to be Bottom. Bottom is also enchanted, so that he has an ass's head. Titania eventually capitulates and gives up the boy, so that peace is restored.