Horse Diaries is about a horse named Black Cloud. The story begins when he is born. He explores around the meadow as his mother keeps them from harm. After discovering many things throughout the meadow, they go back to the herd of horses. He meets his father and some other colts and fillies. After many days of playing, grazing, drinking, and sleeping with the other foals, a strange machine flies above their herd. When all the other horses go running, Black Cloud follows. He runs from the machine, which his mom calls a helicopter, for hours on end. Soon, many of the horses begin to fall and never get back up. When the machine leaves, the horses stop near a foul-tasting creek. Many horses are captured by humans. What will happen to Black Cloud?