Ep 4. Kick the Ballistics

In the fourth episode of Castle season 4, titled "Kick the Ballistics", the team at the 12th precinct is called in to investigate the death of a young woman who has been shot at a protest rally. The woman, Monica, was an outspoken advocate for social justice and had been at the rally to support a new policy to combat police brutality.

As the investigation progresses, Castle and Beckett discover that Monica's murder was not a random act of violence but a targeted killing. They soon realize that Monica was not alone in her advocacy and that the other members of her group may also be in danger.

With the help of Ryan and Esposito, Castle and Beckett track down the other members of Monica's group and find that they have all received threatening letters warning them to stop their activism. From the letters, they are able to deduce that the killer is someone with ties to the police department and a vested interest in keeping the status quo.

As the investigation hits a dead end, Castle suggests that they bring in a firearms expert to analyze the bullet that killed Monica. This leads them to Dr. Kelly Nieman, a notorious ballistics expert who has worked on high-profile cases in the past. Dr. Nieman's analysis reveals a startling discovery that sends shockwaves through the team.

Meanwhile, Castle is also dealing with some personal drama as his teenage daughter, Alexis, has decided to move out to go to college. Castle is reluctant to let her go but eventually realizes that he needs to let her spread her wings and find her own path.

In the end, Castle and Beckett are able to crack the case and bring the killer to justice. They also realize that their partnership is stronger than ever as they navigate the complexities of their personal and professional lives.

Overall, "Kick the Ballistics" is a gripping episode that tackles complex issues of social justice, police brutality, and gun violence. The episode is expertly crafted with suspenseful twists and turns that keep the audience guessing until the very end. Fans of Castle will not be disappointed.