What is the mystery of Beware's name? To Lily, who has outgrown her pony, the mare Gramp brings home seems to be the answer to her dreams. But Gramp is uneasy. He can't help wondering why the mare is called Beware.

Under Gramp's cautious supervision, Lily and Beware get to know each other, and soon she can truly claim the horse as her own. And when the mystery of Beware's name is finally revealed, Lily is able to handle the situation with the skill of an expert.