Helluva Boss

The enthusiastic imp Blitzo and his subordinate employees—Moxxie, Millie, and Loona—run an assassination agency called Immediate Murder Professionals (I.M.P.). The group is shown discussing how to drum up business after mistakenly shooting a child named Eddie on their most recent assignment. During their meeting, I.M.P. argue over different topics, including Loona not contributing to the business, and Blitzo stalking Moxxie and Millie outside of work. Some backstory is provided in the form of a flashback, where Blitzo steals a book from Stolas, a Goetial demon of Hell, after having sex with him; the book is what allows I.M.P. to travel to the human world to carry out their hits. In the end, I.M.P. receive a message from their most recent client confirming that Eddie was the right target after all. They kill him, and reconcile while dismembering him together.

School teacher Mrs. Mayberry discovers her husband is having an affair with a woman named Martha. In a fit of rage, she kills her husband and injures Martha, before committing suicide. Martha is praised for surviving the attack and gains publicity and wealth. Mrs. Mayberry, now a demon condemned to Hell, hires I.M.P. to kill Martha. Moxxie is hesitant about killing a mother, thus ruining a supposedly innocent family, so he knocks Blitzo's gun off-course as he shoots. This alerts Martha and her family, who reveal their true nature as murderous cannibals, who then proceed to chase the imps. Blitzo flees, but Moxxie is captured by the children, and Millie is knocked unconscious by Martha's husband, Ralphie.

Blitzo initially evades a shotgun-wielding Martha, but Martha overhearing a sudden phone call from Stolas results in his capture. He and Millie are tied up by Martha and Ralphie, who plan to kill them. Moxxie escapes from the children and kills Martha, saving Blitzo and Millie, while Ralphie runs away. As Blitzo and Millie return to Hell, Moxxie stays behind in order to kill the rest of the family. However, he decides to spare them and calls the local police to deal with them. Instead of peacefully arresting the family, though, the police blow up the house and kill Ralphie and his kids. Back in Hell, Blitzo, Millie, Loona, and Mrs. Mayberry celebrate the successful mission, while Moxxie sits, horrified that he caused the death of an entire family.

Stolas' wife Stella fights with him after learning about his affair with Blitzo. Wanting to get out of the house, Stolas takes his moody teenage daughter Octavia to Loo Loo Land, an amusement park that she enjoyed as a child, and hires I.M.P. as their bodyguards. Blitzo watches over Stolas and Octavia, while Moxxie and Millie enjoy themselves at the park.

Stolas takes Octavia to watch a show featuring the animatronic jester Robo Fizz, but she runs away, fed up with her father's constant flirtations towards Blitzo. Stolas follows her, leaving Blitzo to get into a fight with Robo Fizz, a former co-worker of his. Stolas follows Octavia to a funhouse ride, where she tells him that her home doesn't feel like home anymore because of her parents' arguments. Stolas tries to explain his failing relationship with her mother but cannot find the words to do so. Octavia admits that she fears Stolas will leave her behind in favor of Blitzo, but Stolas assures her that he will never leave her. After their conversation, Stolas decides it's time for them to leave, as Blitzo and Robo Fizz's fight sets the rest of the park on fire.

I.M.P.'s company parking space is stolen by Blitzo's pop-star ex, Verosika Mayday, so he challenges her and her posse of succubi to a bet: if I.M.P. can kill more people than Verosika's group can have sex with in one day, Verosika will have to give up the parking space. With partying spring-breakers as targets, Loona disguises herself as an attractive Goth girl to lure victims for I.M.P. to kill. However, she abandons the challenge to flirt with Verosika's hellhound, Vortex, as Verosika's also-disguised group hypnotizes the remaining spring-breakers into having sex with them. An argument arises between Loona and Blitzo after he intervenes between her and Vortex. She scolds him for treating her like a child, and a heartbroken Blitzo storms off, abandoning the challenge as well.

Moxxie and Millie take the challenge into their own hands and continue killing people, but some humans catch Moxxie and throw him into a beer barrel. As Millie rescues the drunken Moxxie from the barrel, a fish mutated by a beer can Verosika threw into the ocean attacks the beach. Millie kills the fish monster, and Blitzo uses the incident to blackmail Verosika into forfeiting the challenge. I.M.P. returns to Hell to reclaim their parking space while Verosika and her team are arrested by the human police.

I.M.P. is hired by crazed inventor Loopty Goopty to kill his business partner, Lyle Lipton, for taking credit for the aging machine that killed him. Lipton, who was also affected by the aging machine, is now a decrepit old man who no longer sees a point in life. Just as Lipton is about to kill himself, three cherubs — Cletus, Keenie, and Collin — arrive in order to convince him that life is worth living. They take him to see joyous things, such as nature, childhood innocence, and love, but I.M.P. follows the group and sabotages all of the cherubs' plans.

After I.M.P. foils another attempt to help Lipton in a theater, a fight breaks out between them and the cherubs. Lipton, seeing the amount of trouble that the cherubs and the imps are going to over him, realizes the significance of his life and decides he wants to live, only for the cherubs to accidentally crush him under a piano. The cherubs are promptly exiled from Heaven by their superiors. I.M.P. returns to Hell, believing Lipton's soul went to Heaven. However, just as Goopty confronts them for failing their job, Lipton arrives in Hell and reconciles with Goopty.

Blitzo agrees to join Stolas in the Harvest Moon Festival, a festival showcased in the Wrath Ring of Hell. I.M.P. stays with Millie's parents, Joe and Lin, for the duration of the event. Moxxie struggles to impress them, much to the amusement of their farmhand, Striker, who quickly makes friends with Blitzo. Moxxie, Blitzo, and Striker compete in the festival's annual Pain Games, but Moxxie quickly loses each of the events. After Blitzo and Striker are both declared winners, the former invites the latter to join I.M.P. Disheartened, Moxxie returns to the house, but discovers that Striker is planning to assassinate Stolas. Moxxie and Millie try to stop him, but Striker overpowers them and locks them in the cellar.

After encouragement from Millie, Moxxie breaks out of the cellar and sets off to find Striker. As Striker is about to kill Stolas, Blitzo confronts him. Striker attempts to convince Blitzo to turn on Stolas and side with him before Moxxie arrives. Outnumbered and injured, Striker escapes. Later, as I.M.P. prepares to return home, Moxxie stands up to Joe and Lin and earns their respect. Meanwhile, at a motel, Striker informs his client, Stella, of the failed assassination attempt, who orders him to try again.

While on a mission, Blitzo and Moxxie are captured by Agents 1 and 2, members of the organization D.H.O.R.K.S., who have been monitoring the actions of I.M.P. on Earth. The two are taken to a secure facility and interrogated. The agents eventually use a truth serum on them; however, this causes the imps to suffer hallucinations surrounding their own personal issues. They subsequently reconcile their grievances with each other when the drug wears off.

Meanwhile, Millie and Loona infiltrate the facility and fight their way through D.H.O.R.K.S. agents to save Blitzo and Moxxie. Once the demons are reunited, they fight off the remaining agents and, although they manage to kill most of them, are cornered and held at gunpoint by Agents 1 and 2. I.M.P. is saved by Stolas, who possesses Agent 2 and forces the dead agents to summon him. Stolas and I.M.P. return to Hell, leaving Agents 1 and 2 alive. However, the Agents discover that security cameras recorded the carnage in the facility, and they now have enough evidence to prove that demons exist.

For their wedding anniversary, Moxxie takes Millie to a club run by Asmodeus, a high-status demon in the Lust Ring of Hell. Blitzo tries to enter the club to stalk them, but learns that the restaurant is for couples only, so he reluctantly asks Stolas out on a date, much to the latter's excitement. When Moxxie goes onstage to perform a love song he wrote for Millie, he is interrupted by Asmodeus and the restaurant's entertainer, Fizzarolli, who are disgusted by his "sappy" song and point out that their establishment is about lust and depravity. Blitzo tries to come to Moxxie's defense, only to be humiliated by Fizzarolli and Verosika about his disastrous love life, while Stolas is outed for his affair with a low-status imp.

Despite Asmodeus shaming Moxxie and Millie (and ultimately kicking them out of the club), Moxxie's song is well received by the other diners and the two end up enjoying their night out. Meanwhile, Blitzo and Stolas return to their homes dejected, where the former has a breakdown while looking at old photos of his friends and family.