Bibi Blocksberg visits her friend Tina Martin at the riding stables during the summer vacation. This year there is to be a special horse race organized by Count Falko. However, the two friends run into trouble when Sophia von Gelenberg from an elite boarding school at Falkenstein Castle, a participant and close acquaintance of the house, arrives and tries to steal Tina's boyfriend Alexander. The shady businessman Hans Kakmann is also up to no good, and it's not just the foal Socrates, known as "Socke", he's after. Bibi tries to save Alex and Tina's relationship on the one hand and expose Kakmann's business practices on the other. But even witchcraft can't prevent her from turning everyone against her, Count Falko enrolling his son in boarding school and Kakman offering to buy the foal "Socke".