Patient Zero hadn't just lost a dear friend or a maid. She had lost everything. Her lover, all of her friends, her children, her parents and siblings, her neighbors, and her people. As if that wasn't enough, she had also doomed her entire world.
What had he lost? One person.
He still had his family. He still had his friends. He still had his familiars. He still had a home to return to.
"I-I'm sorry," he started saying, tears welling up in his eyes again as he returned Patient Zero's hug.
How could she claim to know his feelings? No. How could he dare to question that claim?
Patient Zero understood the feelings in Zach's apology. He wasn't apologizing for being rude to her. That certainly wouldn't have been enough to make him cry.
He was apologizing because he had made light of her grief. He was apologizing because he didn't know what else to do.