A Murderous Affair in Horizon Tower Episode 3

The autopsy report shows Carbon monoxide poisoning. The detectives deduce that she was first knocked out and then poisoned. The investigation continues with an interview with Lin Da Sen, Mei Bao's neighbor, and landlord. Mr. Lin is an architect. He reveals that he and Mei Bao were neighbors in their childhood and he frequently hung out with her and her brother. He also reveals Mei Bao may have been a kleptomaniac since childhood. Lin Da Sen insists that they were not romantically involved. However, the detectives find out that he personally bought an expensive mattress for her loft and they suspect there was more to their relationship. Flashback to two years earlier, Da Sen's wedding: Da Sen's wife's family are rich and prestigious and he feels out of his depth around them. On the night of his wedding, Mei Bao calls him and they meet. (Source: Autumn carrot at MyDramaList)