Young Lucy, exhausted from years of experimentation in a laboratory, meets the devil Rudolf. Instead of the standard "soul trade," he offers her freedom, revenge, and even a place to stay—first just warm food, then an escape, and finally a sanctuary in his dark castle.

Lucy, distrustful of everyone, gradually agrees—not because of the promises of power, but because for the first time in years, someone has given her a choice. The devil, who wanted to get his hands on an "interesting experiment," falls into his own trap — he becomes interested not just in her temptation, but in her as a person. And Lucy finally finds not only freedom, but also a place where she can be weak.

Rudolf sat quietly in his chair by the fireplace, reading a book he was interested in, while the black cat lay on his lap, purring from affection.