Louis was Rowena's fiance.
After apparently breaking up with Ben, Rowena began dating and eventually became engaged to Louis. However, Louis was a scammer, and not only did he cheat on Rowena with a rich heiress named Mona Levin, he also had Rowena's background investigated.
He was disturbed to find that Rowena had lied about her past, and while he could not find out who or what she truly was, Louis decided to be honest about his affair and break up with Rowena. Despite this, Louis admitted that his own heart was still fond of her, but he did not want to be with a woman who had no fortunes for him to take.
During his argument with Rowena, Crowley popped into Louis' house and asked Rowena who this man was. Rowena confessed that Louis was her latest fiance. Louis was confused when Crowley addressed Rowena as "mother", but was promptly killed by the demon, much to Rowena's delight.