Beckett continues the search for information regarding her mother’s murder. Lockwood kills McCallister, the other cop who worked with Raglan. At his arraignment, fake cops set off a smoke grenade with Kate and Castle in the courtroom. He escapes on a stolen helicopter.

The detectives come to the conclusion that a third cop was involved after they find doctored files. Ryan and Esposito track down leads, taking them to a bar owned by a former officer who worked with Raglan and McCallister. He tells them that a rookie used to follow them around. Someone named Montgomery. 

Captain Montgomery tells Castle that he is the only one who can make Kate back down. Castle speaks with his mother and Kate’s father about his feelings. 

Lockwood shows up in Montgomery’s home and warns him that he is not keeping up his end of the deal. It’s either Kate or his family. He tells Montgomery to get Kate to the hangar so they can end this. Captain calls Kate and has her meet him there. She realizes he is the third cop but he sends her out of there, having Castle carry her out. Lockwood arrives with three other men and a shoot out occurs. Montgomery kills the three men and Lockwood, but not before Hal shoots and kills him. 

At Montgomery’s funeral, Kate is shot and Castle admits he loves her as she lays in his arms.