If you recall the premise of the movie 'When Harry Met Sally ...' men and women can't be friends without sex getting in the way. Apparently, Alan buys into that theme hook, line and sinker, because just the hint of cordiality and friendship between Lyndsey and Charlie brought out the green-eyed monster in the younger Harper brother.
Truth be told, this was a great development in the ongoing Lyndsey-Alan arc because we finally were given some back-story about her and even some insight into why she's still with Alan. He's the schlub of all schlubs who's even been responsible for burning down her home, and yet she's taken him back. Clearly, she cares for the schmuck. For more on how Alan's paranoia was on full display, including V-8 juice and ketchup, read on.