The famous Welsh conductor David Davies is told that he has three months to live, and his doctor suggests that he goes to take a break at The Halfway House, a small hotel in a remote part of the Welsh Valleys.
Richard French is also on his way to the hotel with his daughter, Joanna. Unknown to him, she has overheard him and his wife, Jill, discussing their plans to divorce.
At the station, they meet up with a young couple, Terence and Margaret, and all four walk to the hotel together. In the Valleys, William Oakley, a criminal profiteering from the war, meets his old friend Captain Fortesque, who has just refused work as a prison governor because he doesn't want to contribute to the war effort. They also travel to the hotel.
At the hotel the landlord, Rhys, seems to appear before Fortesque out of thin air and, surprisingly, appears to be expecting his arrival. Rhys introduces his daughter Gwyneth, who arranges a room for David, who has just arrived.
Former ship Captain Harry Meadows and his French wife, Alice, also arrive, after having argued about the recent death of their only son, Jim. When Alice is unpacking in her room, Rhys tells her that she doesn't need to look for evidence of her son's afterlife.
Meanwhile, it transpires that Joanna has told Jill where she and her father would be staying, and she too is at the hotel. Richard catches Jill flirting with Fortesque and they argue again.
Terence (who is Irish)tells Margaret that he is going to be stationed in Berlin as part of his job, and justifies it by saying that Ireland hasn't declared war on Germany. She hates the idea and says that she won't marry him until he comes back from Berlin.
At dinner, everyone meets at the table and Terence says that Ireland should remain neutral. Alice disagrees, using France's situation as an example. Rhys tells the guests that the hotel was bombed a year ago, and then they all leave. David and Gwyneth talk over the washing up. Gwyneth tells him not to be afraid of dying.
The next day, Harry takes Joanna out on his boat, so that she can pretend she is drowning in order to try and get her parents back together. Instead, by accident she and Harry fall in - but Harry can't swim. Her cries alert her father and Fortesque, who rescue both her and Harry, but on shore Joanna's parents discover that she had planned the whole thing, and they argue again.
Meanwhile, Rhys speaks to Terence and challenges his Irish nationalism, saying that he wouldn't put Wales before the whole of humanity. Gwyneth speaks to Joanna and tells her not to give up trying with her parents.
Inside, Alice conducts a séance to try and speak to her dead son. She hears a voice which she believes is Jim's, but it is the radio, which Harry has just turned on. She flees upstairs in tears, and Harry tells everyone in the room that he just wants his son to rest in peace. Rhys tells him to say that to his wife, and Harry goes upstairs and makes up with her.
Downstairs, everyone listens to the radio, which is discussing last year's news about the fall of Tobruk. David realises that everything in the hotel is exactly one year old. They change the channel, and hear David conducting a performance in Toronto, confirming his suspicions. He warns them to be quick - because last year's air raid will happen and they will be bombed again.
Bombs start raining in, and Fortesque writes to his old regiment asking if they will take him back - he is now fully committed to the war effort. Joanna's parents are reconciled, and Terence decides to fight against Germany. Rhys confronts Oakley and tells him to stop profiting from the war and to follow his heart.
Rhys and Gwyneth tell everyone to leave and live their lives. Everyone files past and recounts what they are going to do in the future. The hotel crumbles into fiery rubble, before dissolving away and leaving the green valleys beneath.
