What Goes Around, Comes Around - S3-E18
Plot hole: Tess sends Jack an airline ticket to visit her in Australia. The ticket reads 'From: Eureka, Oregon, To: Sydney Australia.' Seems odd that a commercial carrier would have a terminal in the most secret town in America. Eureka is a town created by the US government for its top scientists to experiment with new technologies. It is made nearly invisible from the outside by giant holograms. Very few non-residents even know of its existence.