Every winter the big liner Vienna would come to Bigg City Port to pick up supplies and re-fuel. This year however, the harbour was frozen over, so the tugs have to take supplies out as far as Lillie the Lightship, as this was as near as a big ship like Vienna could go to the harbour. Problems begin when Lillie the Lightship runs out of fuel and things just start getting worse when the Z-stacks show up.