Forty years ago, after struggling with long-term youth unemployment, three sisters took part-time jobs as human test subjects to make a living. Due to unforeseen side effects, their faces remained permanently youthful—frozen in their twenties. Now in their sixties but still looking like they are in their twenties, they run a B&B (Bed and Breakfast) called "Versailles" in Seoul. However, after being scammed out of 100 million won, they face eviction unless they can repay the money within a month. One dawn, a once-in-200-years comet collision brings a meteorite carrying a mysterious liquid infused with alien bacteria crashing near the B&B. Soon, a series of suspicious guests gather: a mysterious Japanese YouTuber, a North Korean undercover agent, a prison escapee, and even police officers. An emergency broadcast announces that aliens disguised as humans have infiltrated the B&B—and that a reward of 200 million won will be given for capturing them.