It's a foggy day but the donkey is going up the mountain to take a sweater he knitted to his friend.
Abrams Books for Young Readers sent me a copy of this book to read for review (thank you). It has been published and you can get a copy now.
As he goes, he runs into a goat who informs him there are monsters on the mountain. He doesn't let that slow him down.
Each animal he meets is carrying something and in the fog does resemble a monster. He waits until he can see them clearly and then carries part of their load.
This is a good lesson: Wait until you can see things clearly before you form opinions.