A mysterious filly is spotted inside the castle and ponies wonder what really happens inside the castle.until ponies learn that the small filly was actually Celestia's daughter. Celestia cherish and adore her daughter very much but when danger comes to Equestria, Celestia is forced to do the unthinkable. Her heart will be broken, sacrificing her own daughter for Equestria's safety.

Marinette gives her Miraculous away... now what?