Ep 20. In Extremis

John Reese and Harold Finch must work together again in the 20th episode of the second season of Person of Interest, titled "In Extremis." When a medical student, Caleb Phipps (Luke Kleintank), becomes the latest number of the machine, Harold passes the responsibility of saving him to Reese.

Reese, posing as a member of the NYPD's bomb squad, quickly tracks down Caleb, who has just stolen poisonous chemicals and a pressure cooker from his lab. Not knowing the whereabouts of his mentor, Dr. Richard Nelson (John Doman), Caleb believes that he is staging a terrorist attack in New York City to get attention on a groundbreaking discovery they have made. Reese prevents Caleb's plan from coming into fruition and eventually finds Dr. Nelson as well.

However, things take a turn when Caleb's health starts to deteriorate after exposure to the deadly chemicals. Reese calls in his old acquaintance, Dr. Megan Tillman (Annie Parisse), for help. Dr. Tillman is a skilled surgeon and walks Reese through the necessary procedures to save Caleb's life without any medical equipment. Meanwhile, Harold goes to the hospital to personally retrieve Caleb's medical files and finds himself in a life-threatening situation.

The episode explores the theme of what it means to be a hero and pushes both Reese and Harold to their limits. The stakes are high, and the clock is ticking as they race against time to save Caleb's life. Reese, being a trained operative, is physically capable of handling any situation, but the real test comes when he is forced to step out of his comfort zone and rely on his intuition and resourcefulness to perform a medical procedure. Harold, on the other hand, must face his own fears and take action to save his friend's life.

Additionally, the episode also tackles ethical questions surrounding medical advancements and their use. Dr. Nelson's attempts to further science through illegal means prompt an examination of the morality of his actions and the consequences they bear.

Overall, "In Extremis" is a thrilling and thought-provoking episode that highlights the strengths and weaknesses of the show's main characters. It showcases their perseverance, intelligence, and ingenuity under pressure, making for one of the most memorable episodes of the series.