When I went to talk to Harlow I got the option to say that I had already killed Trask which wasn't true. I looked him up and went to where she should have been and only found his body. My guess is that he was killed by canids (those were nearby) and the game registered him as being killed by me. Looking at a walkthrough, apparently Trask was supposed to give me the location of some papers but I can't access the papers because he didn't tell me where they were. Now the only way to complete the quest is to just kill Harlow, but I don't want to do that.