When Doug locks the house and tells Dylan to keep everyone safe, Dolly manages to sneak out. Dylan tries to overcome his fear of the Boom Night (nicknamed for New Years Eve) in order to find her.
Dylan is screaming in front of a poster in the park advertising "Boom Night", and frets over getting all of the pups rounded up to go home and hide from the fireworks. Dolly is skateboarding around the park and hanging out with her friends, Fergus, Sid, and a rat. Fergus offers that she stay out with them tonight on the Barge, but Dolly is nervous as she has spent every prior Boom Night with her family at home. Dylan insists that she needs to go home and that the night is about "surviving". Fergus pulls his attention to Dorothy, who is trying to grab a stick in the bonfire pit. As Dylan tries to retrieve her, Fergus insists that he'll see Dolly that night, and she smiles in response.
Dylan attempts to pull the stick out of Dorothy's mouth, but she lets go and he falls back into the bonfire pile. He remarks that it is a "waste of perfectly good sticks" and is hounded by the pups as "stick" is a trigger word. He is able to push all of the pups to the house. Doug greets them all and ushers them in to get earmuffs given out by Delilah. Doug starts breaking down at Delilah's feet over the night, and Delilah comforts him. She continues handing out earmuffs.
Dylan remarks there are only 4 and a half minutes until the fireworks begin, and Dolly sics a group hug onto him. Delilah insists that this is the busiest night of the year for both her and Doug, but that she has full faith that Dolly and Dylan will keep the pups safe. Dylan reiterates that Dolly going outside tonight is a ridiculous and unsafe idea, and finds that Dorothy has taken his helmet. He is given bunny earmuffs instead. Doug has a tearful goodbye with his pups as he goes off to work.
With the parents gone, Dylan tries to command all of the pups to listen to him. Dolly calls him "Commander Safetypants" and mocks his commanding tone. Dylan mocks her back about going to hang out on the barge. Dolly insists that no one needs to know about her leaving, but Dylan retorts that he will know that she has left and insists that their parents will find out. He orders her to stay put.
She is about to retort back, but Dorothy comes to her feet, so she plays like she's going to stay home. She asks if Dorothy can hear her, to which Dorothy shakes her head "no". Dolly sighs and decides to make some "anti-explosion gear", and Dorothy follows with a determined look on her face. Dolly's gear ends up being loads of tennis balls glued in a suit and a helmet, and she bounces down the stairs as she prepares to leave. She finds Dorothy has gotten stuck in her suit during her bouncing, and tells her there's no "too safe tonight". Dorothy giggles and is ushered upstairs so she doesn't see Dolly leaving. Dolly leaves once she no longer sees Dorothy, and leaves the door open as she bounces away. Dorothy comes out from around the corner of the stairs and stares at the open door. Dolly bounces down the street and remarks on how protective her gear is, but slams into a trash can and slides down onto the sidewalk. She states that she's fine.
Dylan is preparing the pups with less than two minutes until the fireworks begin, but discovers that Dorothy is missing. He slips on Dolly's skateboard and discovers that the door is open as he falls down the stairs. He has a fight with his nervousness and decides that he must leave the house to find them. He gears up and begins searching the streets. He runs into some firecrackers on the ground and is startled.
Meanwhile, Dolly has arrived at the barge, and tells herself to "just be cool" as she approaches. She bounces off several objects before landing in front of Fergus, tennis balls going in every direction. Fergus remarks that her getup is "a lot of fetching". Dolly mistakes Dylan falling down for the start of the booming, and states that she should have stayed home as she hides. Fergus recognizes Dylan and states that Dolly is hiding on the barge. Dylan tells her that they need to grab Dorothy and get home, to which she insists that she doesn't have Dorothy and wasn't aware she had left the house. The two fight as Dylan blames her for allowing Dorothy to leave the house. Fergus reminds the two that Dorothy was enchanted with a stick in the bonfire pile.
The two go to the park to look for Dorothy, sneaking about on the way to avoid their dad from spotting them. Once at the park, the two become nervous with the commotion and large crowd. Dylan bumps into the bonfire pile and mistakes a white flag at the top for Dorothy. Dolly sees his mistake and tries to yell for him to get off. Dylan realizes his mistake at the top, unaware that the humans are about to light the pile on fire. Dolly sticks her paws in some fountain spouts on the ground to propel herself up. As the pressure builds up, Dylan sees Dorothy on the top of their building without any earmuffs, watching the park. He tries to go down the pile, but is ushered back up by the building smoke. Dolly is propelled up by the fountain pressure and knocks Dylan off of the pile into a bundle of leaves. As they leave, they spot Doug making noises in his firetruck. He spots them at first, but as he rubs his eyes, they replace their spots with trash and he shrugs. The two enter their building and run up the stairs to Dorothy.
Dolly is stuck in the entry to the top, but calls out a trigger word, "ball", and the onslaught of pups is enough to help her break free. Dylan covers Dorothy's ears as she coos at the fireworks. Dylan opens his eyes slowly to see that these fireworks were the source of the booming the whole time, and is immediately in awe at them. The rest of the pups ooh at the fireworks as Dylan remarks that none of the pups' heads have exploded. Dolly remarks that You've "got to love this boom town". Dylan finishes with "Especially on this Boom Night".
In the Middle East and South Africa, the episode premiered on December 14, 2018. In Germany, the episode premiered on the next day. In Belgium and France, the episode premiered on December 16, 2018. In the Czech Republic and Hungary, the episode is set to premiere on December 21, 2018. In Poland, the episode will premiere on the same day. In Spain, the episode will premiere on the next day.
This episode is said to be a parody of The Purge franchise.
Because of the location of the show and the autumn colors of the park, it is safe to say that the inspiration for the episode stems from "Guy Fawke's Night", a holiday celebrated in the UK.
During the search montage, Mr. Fuzzy can be seen, still with the vendor who the Dalmatians hooked him up with.
This is the last episode to air in 2018.
The image gallery for Boom Night may be viewed here.