Richard, a broke, sharp-tongued black-market vet, gets evicted from his rundown flat and is hired at an astronomical rate by the mysterious noblewoman Catherine to be the night keeper of Ashford Manor. His plan is simple: coast through the shift, collect his paycheck, and get out. But when he stumbles into a forbidden zone to save a mortally wounded Abyssal Royal Squid, he inadvertently completes the seal on an S-class calamity—and the overflow magic floods straight into him. Suddenly, the entire world thinks some legendary hidden powerhouse just obliterated the disaster. He keeps healing beasts for the money, but the more he heals, the stronger he becomes, earning him an A-rank agent badge from the DMTC. As he digs deeper into the manor's secrets, he uncovers the horrifying truth—this is no mansion, but a crumbling prison built on the souls of fourteen ancestral guardians, barely containing thousands of calamities. And he has been chosen as the sole heir to inherit their power and end a century-long nightmare.