What do you do when a sex offender moves into your community?

I think it's time for us all to discuss the following issues:

1) What do you do when you arrive at a friends home for shabbos and another guest is also there who is known (or suspected) to have molested children in the past?

• Do you say anything to your host or other guests?
• Should you stay or leave?
  

2) What do you do when you know there's a sex offender in your community and your rabbi is covering for them?

3) What do you do if you are in a public place, children are present and a suspected child molester is also present?

4) What do you do when a friends child is suspected of molesting children or sexually assaulting another?