I wonder if he noticed us doing so. I wonder how it feels when people lock their doors at the sight of you. (Para. 13)
Meaning: I don't know whether he realized that we locked the doors because we saw him. I don't know how you feel when people lock their doors as soon as they see you.
at the sight of: on seeing
She cried at the sight of a dog. 她一见到狗就叫了起来。
People jumped with joy at the sight of the ship coming to the port. 看到船驶入港口，人们高兴得跳了起来。