Prior waits outside in the cold and the dark for a sign from Sarah's window. When he sees it, he climbs up the side of the wall and makes his way into her room. They cannot make too much noise because her landlady does not allow her to have men in her room. He looks at a photograph on her dresser and wonders about her family. Sarah assures him that her mother will like him, though she might like him more if she thought he was going back to the war. Prior considers telling Sarah about his war memories, but he decides against it. He needs her to remain ignorant so that he may be consoled, so that he may find, in her innocence, a place to hide. Prior tells Sarah he loves her, and she responds that she loves him too.
Sassoon and Owen sit in the corner of a lounge at the Conservative Club drinking brandy. They laugh together over a book of very bad poetry given to Sassoon by the author, an admirer. Sassoon gives the book to Owen as a gift. They talk for a moment about how Rivers is leaving and how dreadful it will be for Owen at Craiglockhart without Sassoon or Rivers there. Owen would like to stay at the hospital another month, but he realizes that he too must soon give up his bed to another soldier who needs it more. Sassoon gives Owen a letter of introduction to Robert Ross, a Canadian authority on art and Oscar Wilde's literary executor. Sassoon pats Owen on the back and says goodbye. Owen is left with a tremendous sense of loss.
Rivers goes on his last round to say goodbye to his patients before he leaves for his new job in the morning. He is leaving in a blaze of glory, as Willard is finally walking again and both patient and staff credit Rivers with achieving a medical miracle. Rivers goes to say goodbye to Sassoon, who has spent the day with Lady Ottoline Morrell, a well-known pacifist. Sassoon has remained firm in his decision to return to the war, but Rivers is left to wonder whether it was the hospital, and not the war, that has broken Sassoon's spirit.
Rivers goes to London, where he finds his lodging suitable. Unfortunately, he is unable to sleep well, as he is kept awake by the sound of guns through the night. He finds his work in the Air Force hospital extremely interesting. Although pilots do have occurrences of nervous breakdowns, they are not nearly so common as they are in the men who man observation balloons. This evidence supports Rivers's theory that it is "prolonged strain, immobility, and helplessness" that causes the mental damage, not sudden shocks in men who were already predisposed to mental illness. Rivers reflects that this discovery might explain the high occurrence of anxiety neuroses in women in peacetime, as their confined lives allow them fewer opportunities for control and constructive action.
Rivers feels he must accept an invitation from Dr. Yealland, a well-known London psychiatrist, to visit the National Hospital. Although he is tired, Rivers goes to meet with Dr. Yealland and follow him on his rounds. He watches as Dr. Yealland assumes an arrogant, almost godlike manner, refusing to speak with or take questions from his patients. Rivers notices that many of the patients show signs of depression, and he learns that no work is done to follow up on the patients after they leave the hospital. Dr. Yealland achieves his "miracle" recoveries by using electro-shock therapy on the patients. In one case, a patient named Callan, Yealland has applied very strong electric currents to the patient's neck and throat and has even touched lighted cigarettes to his tongue in an attempt to get him to speak. Because this has not worked, Yealland concludes that some patients just do not want to be cured. Yealland says he will allow Rivers to witness a treatment if he promises not to be a "sympathetic audience."
The contrast between the methods of Rivers and Yealland emphasizes the different approaches to the concept of healing. Because the treatment of mental problems was in such an early phase when the war broke out, psychiatrists were allowed alarming latitude in the methods they invented to treat their patients. Electro- shock therapy was one method that was thought to be extraordinarily effective in "curing" shell-shock. When Rivers witnesses Yealland's method, he cannot help being alarmed at the pain Yealland eagerly inflicts upon his patients. Equally horrible is the arrogance and god-like demeanor Yealland adopts. Just like in the war, Yealland's patients are powerless to resist the torture being forced upon them, and it is not helpful that Yealland makes them feel even more victimized by his powerful and superior attitude. Like many doctors of his time, Yealland cannot accept that there is something mentally wrong with the men. Because he assumes their problems must be physical, he does not bother to treat their minds. Rivers is left to wonder how effective such a cure can be.
Though Regeneration is a fictional work, Barker concentrates on maintaining realism. The details she includes, both touching and horrifying, work to build a more realistic picture of the time and experiences of the First World War. Not all psychiatrists were comforting and understanding, as Rivers was. Often, patients only worsened with treatments meant to heal them.