-Shauna Taylor is tortured and killed and Simon Doyle is spotted leaving the scene. Doyle swears he didn't kill Shauna. He was sent from the future to save her. Castle love the theory. Beckett doesn't believe a word of it.
-Doyle claims that in 2031 there is a massive energy war and what happens now could change the outcome and kill millions of people in the future. Then he disappears from his jail cell.
-Garrett Ward, another supposed time traveler killed Shauna searching for her brother, Dr. Malcolm Wickfield. Wickfield inspired a student, Paul Deschile who Doyle claims later comes up with a way to end the war. When Garrett goes after Paul at a planetarium, Beckett and the team stop him.
-Doyle tells Castle and Becket that in the future they do get married. Castle writes serious literature. Beckett becomes a senator and they have three kids.
-Castle finally tells Alexis that Pi has to go. She says that she and Pi are getting their own apartment and she moves out. Castle is heartbroken that his little girl has grown up.