At the beginning of Sweet Tooth season 3, we saw that Birdie got to know that Gus was alive. It was a huge relief for her, but at some point, she also started to feel restless as she didn’t know in what condition her child would be. Also, Birdie’s research had come to a point where she had run out of ideas. She didn’t know if her quest would lead her anywhere or if she would ever find a cure for the Sick. She started questioning her own decision to come to Alaska and leave her family behind. At that juncture, she thought that maybe she would have been more happy if she had stayed back with Gus. All these thoughts clouded her mind, and that’s when she made the decision that she was going back to be with Gus. She knew that in the kind of world they lived in,...