Julia lives on the sixth floor of Mouse Mansion in a tiny room with her mother. Julia is super curious and very stubborn. Whenever she gets bored she leaves the house and goes outside, looking for her best friend Sam. Sam lives in the middle of Mouse Mansion with his mum, dad, brothers and sisters. Sam is super shy and very well-behaved. But when he is with Julia, Sam finds himself doing things he normally wouldn't dare. The two mice are inseparable. And together they get up to all sorts of fun ...