In Chicago P.D., members of the Intelligence Unit of the 21st District of the Chicago Police Department have to deal with new (and at times recurring) threats every single episode. The nature of these threats and how they handle them mostly determine the quality of the episode. Other times, it's personal matters revolving around love and family that leave viewers applauding.
Each fan of the show might have their own favorite episode each season but there are those that are universally considered the best. With the police procedural providing more than 15 episodes each season, it can be difficult to pick a favorite but most fans agree on a couple. The fan consensus can mostly be seen through IMDb ratings.
"8:30 PM" (Season 1) - 8.2
In the episode that's part of a two-night crossover event with Chicago Fire, members of the Intelligence Unit are called in to investigate after a bomb goes off at the Chicago Medical Hospital. Firefighters also show up but one of them gets badly injured.
As the first major crossover event in the Chicago universe. "8;30 PM" does a great job of blending the best characters from the two different shows. The investigation pulls the viewer in and takes them through twists and turns, with Voight and his team first identifying the culprit as Paul Watts only for it to turn out to be Ted Powell. Themes of revenge and racism are also brilliantly explored since these are Powell's motivations for killing his victims.
"The Number Of Rats" (Season 2) - 8.7
Captain Olivia Benson from Law & Order: SVU arrives in Chicago to help the Intelligence Unit solve a murder case that is frighteningly similar to one she handled decades ago. The episode is part of a three-night crossover event with Law & Order: SVU and Chicago Fire.
What mostly makes "The Number Of Rats" incredible is its unique villain, who prefers donning medical scrubs while committing his crimes, and also enjoys applying green nail polish to his victims. His stylish ways make the law enforcement officers work harder to investigate as they figure there must be meaning to all he does. Even with Benson assisting, the villain proves too smart. Worse is that he causes Nadia's death, a development which is considered the best storylines in Chicago P.D. The melancholy and sense of defeat by the officers makes the hour unforgettable.
"Start Digging" (Season 3) - 9.2
The Intelligence Unit is called in to look into the murder of a girl. More baffling is that she had contact with Voight's son before her death. The episode also sees Voight being offered the chance to become Lieutenant.
"Start Digging" distinguishes itself from other episodes by not focussing so heavily on the shootouts and investigations. Instead, it's more about office politics. While Voight's promotion looks like a win on paper, it's actually a way for his bosses to keep him off the field since they consider his methods too old school and capable of triggering police-related scandals. Since Voight has always been smart, he sees through the whole scheme, leading to a feud between 'boss' and 'bigger bosses.'
"Emotional Proximity" (Season 4 ) - 9.1
"Emotional Proximity" is yet another crossover episode with Chicago Fire and Chicago Justice. In it, Olinsky's daughter dies when a fire breaks out at a warehouse where teens are holding a party. Things become complicated when the warehouse owner kills himself.
The episode milks sympathy from the viewer from the first minute and never stops until the end. Spotting tears in a man who never shows any emotion makes the viewer burn with pity too. Fans also get to see just how good the Intelligence Unit officers are at exercising restraint. In as much as Olinsky is burning with the desire to strangle the culprit, he knows such an action will ruin his career so he hands him over the case to the State Attorney's office.
"Homecoming" (Season 5) - 9.3
Season 5's best episode centers around Olinsky again, who shockingly dies after getting stabbed in prison. Voight has troubles of his own since his brutal methods of policing have made him catch a murder charge. He thus has to make a deal.
Among the most heartbreaking moments on Chicago PD, the death of Olinsky tops them all. It truly rains and pours for him as his death comes only a year after losing his daughter. Once again Voight proves to not be the ordinary type of police officer by executing Olinsky's killer even though he's facing a murder charge. It's the kind of badass attitude that makes fans adore him. Part of the reason he doesn't care about the outcomes of his actions is that they have never really brought him down. He has always overcome them.
'Reckoning" (Season 6) - 9.1
The Intelligence Unit officers have a major headache since Kelto—the candidate for Mayor—has vowed to disband the unit once elected. They thus do everything possible to stop him from ascending to power.
It's a rare occasion where the unit faces off against an antagonist that isn't the typical offender with guns and murder on their mind. The fact that Kelto is using legislation as his weapon puts the officers in a difficult spot since they aren't used to fighting such kinds of wars. They thus fight the best way they know how: by digging up dirt. Since no one is clean, they find out that Kelto has ties to a drug lord. It's game over at that point.
"I Was Here" (Season 7) - 9.0
Burgess follows up on a 911 call about a domestic dispute only to find a dead woman. The killer happens to not only be a violent husband but a sex trafficker who is wanted by the FBI in 6 states.
"I Was Here" sheds light on the plight of women across different but often recurring circumstances. The unfortunate effects of domestic violence are laid out and so is the sexual exploitation of women. Burgess being the star of this particular episode is appropriate, given the female-related themes. Unfortunately, she is also used to highlight another plight: the struggles of child-bearing. While helping a victim, she ends up losing her baby.
"The Other Side" (Season 8) - 9.2
When Burgess is kidnapped, the Intelligence Unit finds itself in a race against time to save her. Emotions run too high that two fan-favorite characters in Chicago P.D., Atwater and Ruzek, opt for fisticuffs after failing to agree on the appropriate strategy to use in rescuing Burgess.
Given how competent there are, the Intelligence Unit members rarely find themselves in a situation where their lives are at the hands of villains but on this occasion, that is the case. Suspense is painted all over the episode, with constant hints that this might be Burgess' last rodeo. In the end, there is relief when she is finally rescued.