The Chronological Viewing Order of Every Major ‘One Chicago’ Crossover

The interconnected television universe created by Dick Wolf intricately weaves narrative arcs across ‘Chicago Fire’, ‘Chicago P.D.’, and ‘Chicago Med’. Watching these collaborative multi-part storylines in chronological order provides a seamless experience as characters respond to citywide crises together.

Initially, early events connected only two series before ‘Chicago Med’ premiered, but later events expanded into massive three-part multi-series emergencies. Following the broadcast order of these interconnected storylines allows viewers to appreciate the complex narrative continuity of the franchise.

The Firehouse 51 Bombing (2014)

The two-part crossover kicks off in ‘Chicago Fire’ with the episode ‘A Dark Day’, where a devastating explosion rocks Chicago Medical Center during a charity road race. First responders from Firehouse 51 spring into action, initiating rescue efforts amid the rubble while evacuating injured civilians and aiding wounded colleagues. The storyline wraps up in ‘Chicago P.D.’ with the episode ‘8:30 PM’, which shifts focus to Sergeant Hank Voight and the Intelligence Unit as they hunt for the bombers. Detectives and firefighters collaborate across the city to locate the primary suspect and defuse a secondary explosive device before more casualties occur.

The Arson / Vegas Crossover (2015)

This investigation begins in the ‘Chicago Fire’ episode ‘Three Bells’, following the discovery of new evidence linking the fatal fire that claimed paramedic Leslie Shay’s life to a serial arsonist. Lieutenant Kelly Severide teams up with the Intelligence Unit to track the arsonist’s movements after uncovering a series of suspicious fires spanning several years. The narrative concludes in the ‘Chicago P.D.’ episode ‘A Little Devil Complex’, where detectives identify the elusive suspect operating under multiple aliases. Intelligence pursues the dangerous pyromaniac through an intense standoff to secure justice for the fallen paramedic.

The Nesbitt Case (2015)

The two-part season finale starts in the ‘Chicago Fire’ episode ‘Spartacus’, as Lieutenant Matthew Casey uncovers illegal operations linked to strip club owner Scott Nesbitt. Sergeant Voight recruits Casey to go undercover to assist the Intelligence Unit in building a solid federal human trafficking case. The plot concludes in the ‘Chicago P.D.’ season finale ‘Born Into Bad News’, where Casey’s undercover role places him in direct danger with armed criminals. Intelligence executes a tactical raid to dismantle Nesbitt’s trafficking organization and rescue Casey from peril.

The Poisoned Victims Crossover (2016)

The franchise’s first official three-way storyline kicks off in the ‘Chicago Fire’ episode ‘The Beating Heart’, where firefighter Christopher Herrmann is rushed to the hospital after a violent stabbing. The narrative continues in the ‘Chicago Med’ episode ‘Malignant’, where attending physicians discover that several dying cancer patients received lethal overdoses of chemotherapy despite being cancer-free. The case culminates in the ‘Chicago P.D.’ episode ‘Now I’m God’, focusing on the Intelligence Unit’s criminal investigation into the rogue oncologist responsible for the deadly treatments. Sergeant Voight leads the investigation into the doctor’s malpractice, revealing personal ties that affect his team as they secure formal charges.

The Apartment Building Fire (2018)

This three-part event begins in the ‘Chicago Fire’ episode ‘Going to War’, as firefighters battle a massive inferno engulfing a 25-story residential high-rise. The crisis transitions to the ‘Chicago Med’ episode ‘When to Let Go’, where emergency personnel manage a sudden influx of burn victims, including Detective Jay Halstead’s critically injured father. The storyline concludes in the ‘Chicago P.D.’ episode ‘Endings’, as the Intelligence Unit determines that the fire was an intentional act of arson orchestrated by a cartel operative. Detectives pursue the perpetrator through the streets of Chicago to hold the cartel accountable for the tragic loss of life.

Infection (2019)

The three-show crossover starts in the ‘Chicago Fire’ episode ‘Infection: Part I’, when a flesh-eating biological pathogen strikes civilians near a university tailgate. The medical crisis escalates in the ‘Chicago Med’ episode ‘Infection: Part II’, where doctors and epidemiologists rush to treat quarantined patients while identifying the engineered bacterium. The narrative concludes in the ‘Chicago P.D.’ episode ‘Infection: Part III’, with the Intelligence Unit tracking a rogue scientist who weaponized the bacteria to target the city. All three emergency divisions coordinate across Chicago to locate the perpetrator and avert a catastrophic biological outbreak downtown.

The Toxic Chemical Crossover (2020)

The two-part crossover begins in the ‘Chicago Fire’ episode ‘Off the Grid’, as paramedics respond to numerous young victims overdosing on counterfeit opioid pills laced with toxic chemicals. Former police officer Sean Roman returns to Chicago to investigate his missing sister, working alongside Firehouse 51 to trace the deadly drug supply. The arc concludes in the ‘Chicago P.D.’ episode ‘Burden of Truth’, where Voight’s unit targets the dealer responsible as the search for Roman’s sister turns into a homicide investigation. Medical personnel from ‘Chicago Med’ also assist by treating victims and analyzing the lethal chemical compounds in hospital facilities.

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