After a wild night at their Yule Ball Hermione has fallen in love with Draco.
This is set during their 5th year at Hogwarts even thought the Yule Ball is in their fourth year. The trick-wizard tournament happened last year tho.
What happens when 100 years ago the Granger and Malfoy wizard families make an arranged marriage for a future generation 100 years to the present day where Draco and Hermione are of age.