I think Gideon did it, probably pretty much the way Detective Graves said he did. I also think Gideon and Eva are being careful, but I don't really think the cops are pursuing it as eagerly as they were when it first happened. I think Detective Graves won't at least, but it is still an unsolved crime so they will still be taking tips and clues. But a precinct in NY would probably have many crimes to investigate and since Nathan was a crazy low life who would have killed Eva, I don't think the police will be actively investigating. But there are some wanting to take Gideon down, whether they are bitter over things Gideon did or even someone still mad about his father. I haven't thought about this next part before until just now, but maybe Nathan was working with someone who wil suspect Gideon killed Nate. Maybe Gideon and Eva are being cautious so no one in the press starts to link together the murder of some random guy at a hotel to Eva and Gideon thus bringing her abuse out front and center. There are so many possibilitles, and I can't wait to read all about it.