Floss is a young border collie who belongs to an old man in a town and loves playing ball with the children in the park. The old man's son is a farmer and needs a new sheepdog to replace Nell, who has grown too old to work, so the old man decides to give his son Floss. Somewhere in her memory Floss knows about sheep and she soon learns how to be a sheepdog. But one day when Floss is on the hillside herding sheep, she sees the children playing with a new ball and can't resist joining in. Meanwhile the sheep escape — and the farmer is very angry. Floss is put in the doghouse, while Nell rounds up the sheep. But after this Floss becomes a very good sheepdog — although, when she has time, she still likes to play ball with the children.