Detectives and private investigators always keep unsolved cases open. Even years later, they'll
always consider the importance of a newly-found clue or fresh information that helps cast new light on a case that has had much thinking time applied to it. Somewhere in your world, it appears you need to go back in time to bring into the open a discussion or some form of negotiation that got left in the 'Unsolved' folder. New information can be applied to alter your or someone else's opinion or attitude - and a new level of agreement can be reached.