After a big war between Su and Ning, a marriage alliance is established, forcing Princess Ning Qian Xi of the defeated Ning nation to marry the Su general's son Xiao Qi Feng. On the wedding day, a ghost in a green dress emerges, which leads to the discovery of a female skeleton in a well at the mansion. The wedding gets postponed while the emperor orders Xiao Qi Feng to investigate the case. Su Qing, Qi Feng's childhood sweetheart, joins the investigation and he really wants to marry. During the investigation, it becomes clear that not one but two parties had plans to assassinate the Queen of Su at the wedding. It also becomes clear that it all relates to an event from 20 years ago and even involves the emperor himself.