Hunson Abadeer returns to Ooo to bond with his daughter Marceline, but will he be able to prove he's changed his soul-sucking ways? 
Finn is needing a new sword, so he enlists the help of Peppermint Butler, who forges a weapon, the Night Blade, and then summons Hunson Abadeer (voiced by Martin Olson) to infuse it with "Nightosphere magic." Released unto Ooo, Abadeer initially tries to harvest souls, but Peppermint Butler binds him with a spell, rendering him powerless. Abadeer then decides to accompany Finn and Jake to the house of his daughter, Marceline the Vampire Queen (voiced by Olivia Olson).
Marceline is getting ready to perform at a concert for a group of ghosts at the Hamburger Hills Cemetery and is frustrated when her father randomly turns up at her doorstep. Although she tries to avoid mentioning the concert so that her father will not attend, the news is inevitably revealed and Abadeer forces his way into her concert. During a performance of Marceline's song "Slow Dance," Abadeer accidentally gets into a brawl with several ghosts. Because Abadeer is still bound by Peppermint Butler's magic, he is unable to defend himself. Finn manages to fight off the ghosts with his new sword, and then Marceline transforms into a bat, grabs her entourage, and flies away.
At the end of the episode, Marceline, Finn, Jake, and Hunson Abadeer meet up with Princess Bubblegum in a restaurant; Marceline thanks her dad for trying to support her, even if he caused a scene.
Throughout the episode, Princess Bubblegum's conniving Cousin Chicle (allied with Uncle Gumbald) disguises himself as a ghost and spies on Marceline to learn her weakness, as Gumbald has identified Marceline as one of Bubblegum's more powerful allies.
- This is Hunson Abadeer's first actual appearance since season 4's "Daddy's Little Monster."
- This episode reveals that the tall, thin guard that opened the door to Gumbald's lab for BMO and Ice King in "Always BMO Closing" was Chicle.
- The Night Sword previously appeared in "Orb" twice: in the title card, and when Finn finds Jake in the dream play.
- Marceline is seen wearing Princess Bubblegum's sweater from the Stakes miniseries when Finn, Jake, and Hunson enter her house.
- Finn's answer to Hunson's second question "Is [Marceline] still half-vampire?" is "yes, but no, then yes again," referring to the Stakes miniseries when Marceline was cured for a short while before becoming a half-vampire again.
- In the flashback from "Everything Stays," when Simon was leaving Marceline, he told her, "I'll arrange for someone to come take care of you." This episode reveals that person was Hunson Abadeer. This makes sense because Marceline is seen spending time with him in her memory of him eating her fries in "Memory of a Memory."
- The venue for Marcy's concert is Hamburger Hills Cemetery, which is where the episode "Ghost Princess" takes place. It is also a reference to the Battle of Hamburger Hill from the Vietnam War.
- One of the heckling ghosts at Marcy's concert says to Abadeer, "What you gonna do, eat my fries?" as a reference to the "Fry Song" from "It Came from the Nightosphere."
- When Marcy steps into the fight, one of the ghosts says, "Vampires can't hurt ghosts, stupid!" Marceline referenced this fact herself back in the episode "Heat Signature" when she said, "Vampires can't beat ghosts. It's sort of a Rock-Paper-Scissors thing."
- Hunson sings "Walkin' in ooo, not suckin' out souls", referencing the song "Stompin' On Ants" from "It Came from the Nightosphere"
- Hunson's flashback reveals how Marceline got the Family Axe and turned it into her bass.
- Olivia Olson released a clip of Martin Olson and Jeremy Shada recording some dialogue for the episode on social media, but then she had to remove it.
- This episode was released early on the Cartoon Network app on December 7, 2017.
- When Finn is shocked, he has two normal arms instead of one normal arm and one metal arm.