As has been stated already, only rogue Harbingers are bad; I'm sure that a rogue Henri would be utterly terrifying. Henri needs to remember his promise to Lucy and his goal of bringing Harbingers back into society. The people of Oasis seem like good people (well, with the one that attached l attacked you being a possible exception) and deserve a chance to experience more than what the Dark Forest has to offer. I also believe that Asher and his sister might be able to help you with your abilities, possibly might know what you are, and (though the killer might be a Harbinger, unfortunately) might even be able to help figure out what/who the murderer is and how to deal with them.

Remind your uncle who he is and what he means to you and represents to others and I think that, while things may initially get worse before they get better, everything will work out in the end.