The prince of Troy runs away with the Greek king and go to Troy together. Love affair possibly?
The king wakes up to realize the queen missing so he sends soldiers to build a 6 story big horse and send it to Troy and infiltrate. The Trojans let the horse in thinking it was a gift rather than a bait, although, some did warn the Trojans.
Once it was night time, the Mycenaean's let in the soldiers through the gates and the Trojans and Mycenaean's went to war, successfully getting the queen and burning Troy down to the ground.