Alenka and her dog Sisinka can't wait to visit their grandmother in the Giant Mountains again. When they find a letter from Krakonoš in the mailbox inviting them to a birthday party at his field, they know that an adventure awaits them with the cats Daša, Máša, the cat Lucifer and the Saint Bernard Karl. Among other animals, the dog Bonny, who does not listen to his owner very much, will appear at the celebration. Will Sisinka also be naughty? And how will the other animals treat Bonny?