Bella wants to learn how to play a musical instrument but can't seem to decide which one. Kobi, Sam and Mali try to help her choose by exploring the many different instruments that exist but there's one particular sound that is inspiring Bella. The only problem is no one knows what the sound is, or where it's coming from.

When the residents of Apple Tree House find themselves surprisingly low on milk, they start to wonder where it's all going. After a bit of investigating, all clues point towards Bella, Sam and a furry little stray cat that they've found.