During a precinct meeting, Terry announces that today is Amy's final day before maternity leave.
There's a blackout in Brooklyn.
Holt and Terry get trapped in an elevator. Amy, as the next highest-ranking officer, has to initiate blackout protocol.
The squad reluctantly calls the fire department to get them out.
Scully and Hitchcock rush to eat all the frozen food before it goes bad.
Holt reveals he has a phobia of elevators.
Jake and Charles go to the site of the power transformer that was damaged. Someone drove into it and ran from the crime scene. Jake and Charles follow the trail and find the drunk driver who fled the scene.
Amy delegates tasks to the precinct. Her water breaks.
Rosa tries to convince Amy to go to the hospital but she insists on staying to help.
Jake rushes to get back to Amy in time for the birth. On the way there, a woman named Dottie walks by the police car and asks for help. She's locked out of her apartment.
Jake offers to drive her to the precinct along with the drunk driver him and Charles are bringing in.
To distract Holt from panicking in the elevator, Terry teaches him dance moves.
There's a traffic jam on the way back to the precinct so Jake and Charles decide to walk. They hear a commotion from a nearby building and leave the drunk driver handcuffed to a railing outside with Dottie.
When they come back, Dottie has shot the driver in the leg for moving. Since he can no longer walk, Charles calls a Tipsy Topsy Trolley to get them all back to the precinct in time.
On the trolley, they interrupt a bachelorette party. The bride offers alcohol to the injured driver. He declines, saying he's two years sober. This leads Jake to discovering that the accident wasn't an accident at all.
The driver drove into the transformer so his crew can raid the banks in Brooklyn.
Rosa tries again to convince Amy to go to the hospital once her contractions get closer together.
Jake and Charles arrest the criminals at the bank, and make them get on the trolley.
The power comes back on.
Amy's out of time: she has to give birth in the precinct. Jake was on his way to the hospital, so he has to rush back.
Scully and Hitchcock prepare a birthing area for Amy.
Rosa and the firefighters help deliver the baby, with Jake making it just in time.
Charles swallowed his pride, and called in Peanut Butter. He got Jake back to the precinct quickly.
To distract Amy during the birth, Terry and Holt do the dance they practiced in the elevator.
Amy and Jake name their child Mac, after John McClane from Diehard.