When a mathematician is killed by a 200-year-old bullet, Castle comes up with time-traveling theories.

A subway worker is found dead after witnessing the kidnapping of a twelve-year-old boy.

The death of a bar owner takes Castle and Beckett back in time to the prohibition era.

An actress playing Nikki Heat shadows Castle and Beckett on the death of a matchmaker. Meanwhile, Ryan plans on proposing to Jenny.

The detective on Beckett's mother's homicide case is killed after telling her he has information.

Castle fights to help an old boarding school friend when be is accused of killing his wife.

With time running out, Castle and Beckett must put aside their differences with Agent Fallon to avert a city-wide catastrophe.

A writer of a popular soap opera is found dead. Castle and Beckett come across cheating husbands, mistresses, backstabbers and a con artist to find the killer.

When a champion swimmer and Olympic hopeful is found dead in a training pool, Castle and Beckett dive in to investigate his murder, and uncover myriad secrets that might have led to his death.

When Beckett's old training officer is killed, she takes off on a solo mission to find the killer. On the plane she runs into Castle who is flying out to the Heat Wave movie set. She lets him help her catch the killer.

Mysterious murder occurs during a beauty pageant and the suspects are plentiful.