Xie Lian was on the mission with Nan Feng and Fu Yao, dressed up as a bride to trick the ghost groom.

Xie Lian was far from the group (Nan Feng, Fu Yao, and some other men) after Hua Cheng walked him to a Ming Guang temple where the 17 kidnapped brides were. Then, the ghost groom (whos actually a woman) appeared and raised their red veils, and Xie Lian ran after the ghost groom that flew off into the dark night and Xie Lian ran out of the temple and ran into a group of men that were trying to get the ghost groom too, and started speaking to them and Fu Yao and Nan Feng came too

(here starts the AU)

Then when Xie Lian and Nan Feng and Fu Yao were speaking to the group of people, the ghost groom wanted to grab Xie Lian, thinking he was a bride