Despite their strained relations, Alexis (Molly C. Quinn) enlists Castle‘s (Nathan Fillion) help to prove a man (James Carpinello) convicted of a murder 15 years ago is innocent before he is put to death in only 72 hours. After meeting with the death row inmate and his girlfriend (Joelle Carter) who has stood by him throughout his incarceration, and finding one or two incongruities to the case, Castle admits it may be possible that the police arrested a very guilty-looking, but ultimately innocent, man.
Doing her part as well, Beckett, who is a little concerned that Alexis never came to her directly for help, enlists Lanie‘s (Tamala Jones) help to retest trace evidence found at the scene which leads Alexis to sit down with the victim’s ex-boyfriend (Alexis Cruz). Ryan (Seamus Dever) uncovers a possible meth lab that existed 15 years ago at the address of a party the victim attended the night of her death. And Castle and Alexis also uncover the fact that one of the students the victim was tutoring, the younger brother (Wes Ramsey) of the man convicted for the crime, may have been present the night of the murder.
However, the slim leads Alexis and her father discover aren’t enough to help a man whose already lost hope and embraced his impending death sentence both for his sake and the sake of the girlfriend he is leaving behind. And, it turns out, the death row inmate has one other reason not to want the investigation to continue any further even if it costs him his life as he believes his younger brother is actually guilty of the crime.
Refusing to give up, Castle and his daughter make one final discovery that proves both brothers are innocent of the crime that one doesn’t remember and the other will to sacrifice his life for. After finding the real killer (Drew Rausch), Alexis and Castle return to New York where the young woman puts Beckett’s anxieties to rest and thanks her future mother-in-law for all her help in solving the case. The condensed time-frame and anxiety help bring Castle and his daughter back together, smoothing over their recent troubles. The episode’s final scene is a nice touch of Alexis officially welcoming Beckett into the family, and the father/daughter aspect of the case works well, but I would have liked Beckett to have been more involved in Alexis’ side of the case rather than just assisting from the police station.