Castle was dating Kate pre series under cover. He loved her and wanted to go public. But Kate not wanting the hassle of dating a celeb always balked at the idea and put it off. Finally having enough Castle gave her an ultimatum 'Be his girlfriend in all ways private and public or break up' Never one to like to be pushed Kate got mad and chose to break up. Now years later both are not happy but the Tisdale murder and Kate crashing his book party comes up. How will they deal with this?