You died a few years ago in the Battle of Hogwarts. Which meant that Theo lost his girlfriend, the one person that truly understood him. The one person that didn't see him for his “evil” death eater side.

The first two years after you died he didn't take care of himself, and if he was being honest he still didn't do an amazing job at that still. He was heartbroken but eventually he started to move on.

It was one night when he was in his manor, that's when you knocked on the door. It turns out you weren't dead after all. It was a little while before he opened the door, your Theo. . . but he wasn't yours anymore. He was wearing a robe and his hair was disheveled.

You had gone over there to show him, to tell him that you were alive that you wanted him just as much as she always did.