When Alan becomes a little too obsessed with building model cars, Chelsea insists that she and Charlie set him up with one of her girlfriends. She sets up a double date, and when Charlie and Alan show up at the restaurant they discover Chelsea's friend is Rose, who had befriended Chelsea to keep an eye on Charlie. Not wanting to scare her off, Rose hadn't said a word about her history with Charlie to Chelsea, and to avoid rocking the boat, Charlie and Alan keep quiet as well. However, as the date progresses Alan and Rose really start to hit it off and they end up spending the night together. Alan realizes the mistake he's made when Rose begins stocking him, and when he suggests they set boundaries Rose gets him where it hurts most.