Sierra Lowe, a genius from the future research institute, dies unexpectedly and wakes up 100 years in the past as the fiancée of Commander Ethan Nacht. Her plan is simple: lay low, earn money, and avoid trouble. And when the ninth wife finally rises to power, she’ll happily step aside. But on their wedding day, Commander Ethan hears her inner thoughts loud and clear: “So this is Ethan Nacht, the guy who secretly slept with the ninth wife?”Ethan was baffled: "Father only had eight wives. Where did the ninth come from?"