Masha can't wait for summer vacation with her dad. He's taking Masha and Sunny to a dude ranch and he has a big surprise for them. But Sunny has other plans. After some creative deception only an evil genius can pull off, Sunny rearranges the summer to include The Newton Camp of Mathematics. As always, Sunny's plans mean chaos for Masha. And who wants to spend the summer at a camp where afternoon activities include math problems indoors? Haven't these kids heard of canoeing and horseback riding?
But it turns out camp is a little bit fun...until Sunny goes missing. When Masha finds her sister, she discovers that Sunny purposely ran away. She knows what dad's big surprise really is, and she doesn't ever want to go home. Sunny has now gotten them both lost, but surely Masha can push that aside so the sisters can deal with this "surprise" together, right?