From The Grey House:
The Red Thread was a membership-only club for humans who had a taste for the unique. There were very few humans who knew that the people dressed as monsters were real. Most never found out unless they were chosen as victims. Vincent had hired five vampires to make sure the monsters did not make snacks out of his paying members.
There were also three bouncers in the club who were to follow Vincent’s rules or die. A human, stationed at the street level door, only let members in. A vampire at the bottom of the steps inside, only let members on the guest list pass. Occasionally, humans and other uninvited guests were able to get past the first two bouncers, but then they would meet Jordan. He sat at the top of the steps and sniffed out the liars and the humans.