In the midst of a heatwave and a citywide blackout, Officer John Nolan and Aaron follow increasingly large leads after they discover criminals hiding at the station. While on duty, Officer Chen makes an alarming discovery after being called to a scene where a pungent smell has wreaked havoc. Meanwhile, Lucy and Harper scheme to get Tim out of his new job and into a more exciting position.

Officer Lucy Chen goes undercover to infiltrate an illegal firearm operation, and Detective Harper and Officer John Nolan work together to solve a mystery involving severed limbs found around the city.

The crossover continues on The Rookie: Feds S01E21 Bloodline (II).