I think it's going to start with where they left off. Then Beckett is going to try to run after Castle. She realizes he already left and she's too late. Then, after that, she goes to the Hamptons to find Gina stomping out of the house, so she goes in. She tells Castle how she really feels and then Castle says the same. After that Beckett's phone rings, there's another mureder. They got to go (with coffee of course)!