In a world plagued by abuse and darkness, a resilient 15-year-old named Keira has one noble mission: to shield her innocent 6-year-old sister from their tormentor until the day they can finally escape their living nightmare. However, fate deals her a cruel hand when she becomes the victim of a heinous sacrificial ritual, and her life is abruptly snuffed out.

But death proves to be just the beginning for Keira as she awakens in the enigmatic realm of Underfell, an ethereal plane that transcends the confines of time and space. Here, she must adapt to her newfound immortality and embrace her role as a Fallen - a valiant guardian entrusted with the sacred duty of shielding pure souls from the wrathful grasp of malevolent angels called Creepers. These sinister beings thrive on the darkest elements of the human psyche, relentlessly seeking to coerce their victims until they devastatingly surrender to their inner demons.

Yet, even amidst this harrowing existence, tragedy strikes once again when Keira's beloved sister mysteriously vanishes, igniting a relentless fire within her soul. Now, her determination is put to the ultimate test as she embarks on a perilous quest to find her sister. Will Keira triumph over her own uncertainties and unearth her sister's fate, or will she be consigned to an eternity of yearning and uncertainty? The answer lies in the hands of destiny itself.