Will and Hazel took a day trip to Brussels, Belgium about a week into their vacation because it only took about an hour and a half to get there by train from Paris. They got to see multiple castles and Hazel's eyes were wide with wonder and she snapped countless pictures.
Just like in Mexico when they walked around the Mayan ruins, she got a little lost in her own thoughts and seemed to frequently forget he was there as she went around with her camera. It was too cute for him to be insulted by it.
He knew what Hazel was like. When she focused on something everything else got blocked out.
That didn't matter. What did was that she was finally acting more like herself. She had barely snapped out of whatever funk she had been in after returning from Georgia.