6x18 - 7th Heaven

Matt and Sarah argue over their wedding plans and their agreement to forego buying an engagement ring and seek Eric for advice, who isn't happy with Matt for getting engaged in the first place. Because of Eric, Matt buys Sarah a fake engagement ring. Mary and Lucy fly to Buffalo for a weekend, or at least that's what Lucy thinks as Mary makes plans of her own. At the airport, Lucy meets a police officer who invites her and Mary to double-date with him and his brother.