Han Sen first thought it was Bao'er that had been tugging his hair, but he was holding her against his chest. Realizing this, he knew it couldn't have been her.
When he saw Snowball's frightened face, he knew something was wrong. It was at this moment instinct kicked in, and he threw a punch backwards to see what may have lurked behind him.
But when he lashed out, nothing met with his fist. And when he looked at what might have been behind him, there was nothing.
Han Sen lifted Bao'er up and said, "Bao'er is there anything behind me?"
Han Sen thought that whatever was behind him might have clung to his back and turned around with him.
Bao'er climbed around to inspect his back and simply said, "Nope."
"No?" Han Sen went over and kicked Snowball. Then, he boorishly asked him, "Did you see something?"