Ella is ten, and loves inventing new things. Leo is three, and loves playing with his big sister. But sometimes being Leo's big sister isn't easy, especially when he keeps getting in the way of Ella's inventions. But when Ella invents a time machine and Leo is accidentally transported back to the age of the dinosaurs, Ella must risk her life to save him. But she soon realizes that not only her little brother, but the fate of the whole world is at stake. Will Ella be able to save her little brother? Will her time machine destroy the past and the future? And will she be able to get them both home before her parents find out what happened?