Kevin wants to go and see his brother, who lives across the valley, and he wants to take his three pets with him, a dog, a cat, and a mouse.
However, the shortest way to his brother's house involves a river crossing, and Kevin only has a very small boat that can carry him and just one of his pets.
He doesn't want to leave the dog alone with the cat, nor does he want to leave the cat alone with the mouse. However, the dog and mouse are great friends.
How can Kevin cross the river to see his brother, and make sure his pets are all happy?