So Katie's real name is Erin, but when her crazy drunko husband arrives and confronts her does he call her the name he has known her by, as his wife?
No, he somehow knows that she's going by Katie now. How does he know that?
Also no one closes curtains in this town, whether they are sleeping alone in a rickety house in the creepy woods. Or whether they are banging in full view of anyone going by.