I don't think it's completely clear what happened, and I don't think you've missed the explanation because of the preemptions. They've dragged this out for months, probably while trying to figure out where to go with it. If it follows the usual pattern, it'll be a huge non-event. From what we do know, it appears Adam might have killed someone while protecting Chance, who was on some sort of case as some sort of federal agent at the time. Apparently, there's some sort of blackmail involved and now, it appears the tiresome Phyllis will get in on the act.
In my pantry with my cupcakes...