Firefighter Kim Ja-hong tragically loses his life while bravely performing his duties. In a unique twist of fate, he is guided to the afterlife by three guardians: Hae Won-maek, Lee Deok-choon, and their leader, Gang-rim. Their mission is to accompany and protect Ja-hong through seven grueling trials across a period of 49 days. Successful navigation of these trials will not only grant Ja-hong a chance at reincarnation but also earn the guardians the opportunity for their own rebirth.
In the first trial, aptly named the Hell of Murder, Ja-hong faces accusations concerning the death of a fellow firefighter who was trapped under debris during a devastating fire. As he stands on the brink of condemnation, a vital piece of evidence emerges: his colleague had urged him to prioritize the lives of civilians over his own desperate attempt to save him. Ja-hong bravely managed to rescue eight others but was forcibly restrained from returning to save his comrade as the structure collapsed. The judge ultimately acquits him, acknowledging his noble actions.
The second trial, Hell of Indolence, presents a character struggle as Ja-hong’s guardians highlight his inherent altruism and hard work. However, Ja-hong inadvertently undermines their arguments by confessing that his motivations were solely financial. Just as he is on the brink of punishment, Gang-rim intervenes, explaining that Ja-hong was driven by the need to support his brother and ailing mother, thus securing his second acquittal.
As the group makes its way to the Hell of Deceit, they come under attack from malevolent ghouls, triggered by a change in the fabric of Hell which indicates that a family member of Ja-hong has transitioned into a vengeful spirit. Gang-rim departs to investigate this mysterious shift, leaving the remaining guardians to continue the procession. Ja-hong finds himself accused of writing deceptive letters to the grieving families of the deceased, including Ji-yeon, the daughter of his fallen colleague. In a display of supernatural synergy, Gang-rim connects with Deok-choon from the mortal realm to advocate for Ja-hong, revealing that he had also penned false letters to uplift his mother's spirits, which helped her focus on healing. The allegations against him crumble, leading to the dismissal of charges.
Gang-rim uncovers that it is Ja-hong's brother, Kim Soo-hong, who has morphed into this vengeful spirit. The narrative twists further when it is revealed that Soo-hong met his end due to a tragic incident involving his partner, Dong-yeon, while on guard duty, a fact that was concealed by their superior, Lieutenant Park. Gang-rim intervenes to thwart a vengeful act initiated by Soo-hong, who is revealed to harbor resentment not towards Ja-hong but directed at Dong-yeon and Park. In a desperate plea, Dong-yeon tips off Soo-hong's mother regarding his buried body, leading him to attempt suicide, but is saved by Gang-rim, illustrating the bond formed through their shared strife.
The trio navigates through the subsequent trials, including the Hell of Injustice and Betrayal, without facing formal judgment. However, in the Hell of Violence, Ja-hong's past comes back to haunt him as he is tried for an incident from their youth where he physically abused Soo-hong during a period of severe neglect. As Ja-hong stands condemned, they attempt to merge his trial with the upcoming Hell of Filial Impiety. During this plea, Ja-hong confesses the deepest of his regrets that stemmed from their financial hardships, revealing that drugs to alleviate poverty drove his action.
In a revelatory twist, Soo-hong and Gang-rim bear witness to their mother enduring maltreatment at the hands of Park at an army base. This ignites Soo-hong's ire, transforming him back into the malevolent spirit he once was, channeling his fury into a devastating tornado until he comprehends the repercussions of his wrath on Ja-hong’s fate.
Upon reaching the Hell of Filial Impiety, Ja-hong is swiftly pronounced guilty. He learns a heartbreaking truth: on the night he contemplated murder-suicide, his mother, Lee Duk-choon, had been awake and willing to accept his fate, as she recognized her burden on the family. In a pivotal moment, Soo-hong, with the aid of Gang-rim and Won-maek, accesses their mother’s dreams, discovering that she had already bestowed forgiveness upon Ja-hong for that dark night. This revelation clears him of judgment, allowing him the chance for rebirth.
Following these trials, Gang-rim becomes aware of the manipulations woven by Yeomra regarding his investigation into Soo-hong. This realization prompts him to confront Yeomra directly and select Soo-hong as the final soul to pass through before their own reincarnation, beautifully encapsulating their emotional tumult and the intertwined fates of these characters.
