Jenny is keen to go after it and gets the horses ready. Mel, Alan and the other workers in the fields are also intrigued and leave their work to follow it. Jenny sets off with Greg not far behind.
Greg and Jenny follow the balloon for a time on horseback but soon lose sight of it. Pet and Ruth discuss the sighting with Charles.
Dave, Jack and Hubert discuss the balloon in the hay barn. Charles interrupts concerned that everyone is coming across as if they need rescuing since they sighted the balloon.
Mel wonders why the sheep have come up to the top of the pasture in a nearby field. Greg thinks they may have been frightened by something. The balloon is spotted hanging off a tree. The group set off to investigate.
The balloonist appears to be dead. Greg frees him from his position hanging up by the balloon's ropes. Alan and the others lower him to the ground.
Mel thinks there may still be a chance to save him and begins mouth to mouth resuscitation. Jenny rides off to fetch Ruth.
Jack makes a coffin for the dead man, whilst Mel, Greg and Jenny discuss why the balloon came down.
Ruth arrives and tells them that the man's neck was broken. They look through the contents of his rucksack and find a camera and some food, including chestnut honey, a speciality of the Cotswolds.
They find a postcard of Chipping Camden and a sketch of Whitecross from the air on the reverse. Mel thinks he was coming down to meet them and wants to got to Chipping Camden to find out more.
Alan and Mel prepare to set off on horseback. Charles advises them not to waste too much time on the trip. Mel suggests that Charles' decision to go back to the land was wrong as there may still be civilisation out there.
Mel and Alan ride off past the field where the balloon crash-landed. Greg, Dave and Hubert are there salvaging it. Lizzie interrupts their work as she has found some binoculars.
Lizzie and Greg meet up with John who has also found a map of England in the woods. Greg is intrigued.
Back home they try to decipher the map which is annotated in a foreign language. They also find more postcards and a Norwegian dictionary.
Whilst en route to Chipping Camden, Mel and Alan discuss the possibility of balloon travel and being able to go anywhere they like. Back at Whitecross, Greg, Jenny, Ruth, Dave and Charles begin to decode the map which highlights tanneries, sugar beat production and barge routes. The map proves that the Norwegian was not sold on the idea of self- sufficiency and instead saw trade and joining up as the way forward.
Mel and Alan meet a man called Seth who initially holds them at gunpoint. Jenny and Greg meanwhile discuss references to hydro-electric power in Bergen in the Norwegian's notebook. Greg is excited about the possibility of industry there. Jenny becomes concerned and tells him she needs him with her.
Seth reveals to Alan and Mel that the Norwegian was called Lars and he knew him and his daughter Agnes. He wonders what has happened to her.
Agnes is lost in some woods and gets into further trouble when she loses her map in the undergrowth.
Seth feeds Mel and Alan and tells them that Agnes interpreted for her father. He explains that the pair came to England by boat having found no-one alive on their first foray to Denmark. Apparently they have industry in Norway but no food to live on, which is why they came to England. They used the balloon in order to map England, an idea thought of by Agnes.
Agnes wakes the next morning and becomes frantic when she realises she has lost her map.
Greg and Charles discuss what the Norwegian's work could mean to them and talk about sending Jack off to Chepstow to organise shipping operations. Pet is concerned by their discussion and fears they are taking things too far.
Mel and Alan return with their news. Jenny tells Pet she is worried about Charles and Greg's plans to federate and the possibility of Greg going to Norway. She tells her that they must stop their plans.
The others interrupt them. Alan tells the group that they need skilled men in Norway. Mel explains about Agnes and insists they look for her. Jenny is now even more worried about losing Greg.
Hubert finds Agnes and tells her about her father's death. He helps her back to Whitecross.
Greg and Charles have become increasingly animated with talk of Norway, trading and continuing the Norwegian's work. Pet speaks out against the plans believing that what they are talking of is not progress and that they haven't just been subsisting until now.
Hubert arrives with news of Agnes. Charles and Mel go to meet her at her father's grave. She explains how she became lost and that her father had come by balloon to find a bull at Whitecross in order to set up cattle breeding at another settlement. She removes the cross from her father's grave explaining that he was not religious.
A meeting is called at which Agnes intends to explain her father's work. Jenny is distraught and talks to Greg about his responsibilities. Greg tells her he loves her and that nothing will part them. Jenny doesn't think he can promise the latter.
Agnes advises the gathering that they should abandon Whitecross as it is too remote. She also advocates killing their sheep and sending Hubert to Hereford. She also tells them that there are 3000 survivors between Whitecross and Grimsby. She goes on to suggest that Jack and Seth should come to Norway to help with the factory there. She explains that they have electric power there but no food. She advises that they must be quick if her people are to survive.
After the meeting, Charles takes a walk and considers the future of Whitecross and tells Jack that he wants him to take Agnes back to Norway. He thinks trading with Norway may be the way forward and that they must take this chance.
Greg and Jenny discuss Norway again. He is prepared to stay with her, but she reluctantly decides that he really should go after all.
Pet and Ruth ponder the future and joke about whether Greg or Charles will become prime minister of a new Anglo-Norwegian alliance. Sally offers Jenny help with the baby whilst Greg is away.
Hubert advises that the wind is right for the balloon journey. Charles tells Greg that he must keep up communications as they are essential.
Greg and Jenny say their goodbyes to each other. Both are tearful and hurting.
Charles and Pet discuss the future. Charles tells her that even if they left Whitecross that they would always move on together.
Preparations for take-off are complete. Greg says goodbye to John and Lizzie and gets into the balloon basket with Jack and Agnes. They wave goodbye to everyone as the balloon lifts off.
The balloon begins to speed away from Whitecross as the community members look on.
Its difficult to like an episode in which the central tenets of the series are under threat. The future of the Whitecross community, and in particular, of Greg and Jenny's long standing relationship are the subject here, as the key players finally pay attention to the world beyond their own.
The discovery of Agnes's dead father and his notes, Melanie and Alan's meeting with Seth and most crucially the arrival of Agnes herself are all events which are set to change the lives of the survivors...