Dead Silence : Two questions I had (spoilers)

So. After the kid humiliated her she killed him,the town thinks she has something to do with it so they kill her. how did Jamie find the dead kids body after five minutes of being in the theater then? Wouldn't the townspeople or cops have investigated the boys disappearance?

Second, did I miss something, or how was the step mom related to Mary Shaw? Why was she using the dad as a puppet.
Meh,just two things I wondered after watching this movie.

About your first question, you're right, there seems to have been a loose end. The second, if you did not perceive his father's wife, it was Mary herself, in her "perfect puppet"

Step mom was Mary Shaws perfect puppet