When Lina's mother decides to spend the summer holidays in the countryside, the eleven-year-old is quite annoyed. Far from the city and her friends, she is supposed to look after her uncle's farm. It's bad enough that she's stuck somewhere in the middle of nowhere, but then this annoying pony Bulli shows up, following her everywhere. However, when some valuable koi carp go missing, Bulli becomes Lina's ally. Together, they set a trap to catch the thief. And afterwards, Lina might just find Bulli a little bit awesome after all.