There is always an evil space race that kills and eat human flesh and we finally got introduced to the space race in this show.  They’re called Reavers which from their description are humans who were driven mad by surviving on the fridges of outer space by killing and eating people.

Reaver attacking an alliance officer

I don’t see how they’re so dangerous considering they die like any other but yet the crew especially Jayne seems to be terrified of them.  I guess thats what we’ll find out in future episodes I hope.  Oh yeah the crazy sister seems to have some sort of telekentic powers of some sort since she was able to tell that the reaver was in that room.