Whether a nocebo can kill is an open question. In the seventies, oncologists in Australia and the U.S. reported cases of patients dying before their cancers were sufficiently advanced to end their lives. “The realization of impending death is a blow so terrible that they are quite unable to adjust to it,” Gerald Milton, the founder of the Sydney Melanoma Unit, wrote.

Between 1977 and 1982, more than fifty Hmong refugees, primarily from Laos, died in the U.S. from sudden-nocturnal-death syndrome, which the community generally interpreted as lethal nightmares, known as dab tsog. Postmortems revealed that some of the victims suffered from abnormal heart rhythms, which could have been exacerbated by the stress of immigration and the fear of an evil spirit crushing their chest in the night. “You can’t help but behave in a way that is the result of having been immersed since birth in a certain set of attitudes and thoughts,” Shelley Adler, the director of the Osher Center at the University of California, San Francisco, who interviewed hundreds of Hmong people about the deaths, told me. During a placebo trial described in 2006, a twenty-six-year-old man swallowed twenty-nine inert capsules, thinking they were antidepressants, in an apparent suicide attempt. His blood pressure collapsed and he was taken to the hospital, where the symptoms abated when he was told what he had taken.

In its first year, the Premonitions Bureau collected four hundred and sixty-nine predictions. Not all of them were frightening. A young Australian living in Beckenham, named George Cranmer, claimed to foresee the winner of the Grand National horse race. His tip for the Derby came in second. But Hencher and Middleton were the experiment’s stars. In the fall of 1967, both predicted a railway crash on a main line heading into London. On November 1st, Middleton had a vision of a crowd on a railway platform and the words “Charing Cross.” Four days later, a passenger train from Hastings was derailed on its way to the station, killing forty-nine people. Hencher was on a night shift, and was taken to the sick bay with a headache at the time of the crash. The Evening News, which was the Evening Standard’s main rival, put “The Strange Case of the Two Who Knew” on its front page. “Quite honestly it staggers me,” Barker said. The newspaper reported, “Somehow, while dreaming or awake, they can gate-crash the time barrier.”

In early 1968, Hencher told Barker that his life was still in danger. In a newspaper interview the following year, Hencher said that he had been convinced that the psychiatrist would die soon, in Yockleton. On February 7th, Middleton had a vision of Barker, in which she saw his head and shoulders on one side and her parents, who were dead, on the other. The image persisted for a week. “Not wishing to alarm anyone . . . I merely said that my parents were trying to tell me something,” Middleton wrote. “I interpreted this as something concerning the doctor.”

Shortly before midnight on February 25th, a fire started in a locked ward for female patients on the second floor of Shelton Hospital. Patients woke up to find the ward filling with smoke and no nurse on duty. The hospital’s fire-training procedures had not been updated for twenty years. Twenty-four women died in the fire. Four survived because they had been locked inside antiquated individual cells with heavy doors, which kept them safe. The outlines of patients who had huddled in the smoke were visible for weeks on the stone floors of the burned-out ward.

The accident helped to catalyze the reform of Britain’s Victorian mental hospitals. “These asylums,” Enoch said. “Anything could have happened.” Enoch was helping a social worker and campaigner, Barbara Robb, to highlight overcrowding and the neglect of older patients. Two weeks after the fire, Barker and a fellow-doctor at Shelton, Mabel Miller, published a survey of chronic patients at the hospital. Sixty-nine per cent had been there for more than five years. “Many of the long-stay male patients were poorly attired; the fronts of their thick serge shirts were heavily stained with food and there was a dearth of ties,” they wrote.

On May 8th, Barker travelled to the U.S. for a three-week lecture tour on aversion therapy. During his visit, he gave a talk about the Premonitions Bureau to the American Society for Psychical Research, on West Seventy-third Street. Robert Nelson, a young executive at the Times, was in the audience, and he set up an American version of the experiment, the Central Premonitions Registry, the following month.

By the time Barker returned home, it was almost summer. Middleton had been worried about Senator Robert Kennedy for months. She had sent her first warning on March 11th. Four days later, she wrote to Barker again: “The word assassination continues. I cannot disconnect it from Robert Kennedy.” In early June, Middleton became frantic. She called the Premonitions Bureau three times on June 4th; Kennedy was killed shortly after midnight. Barker described it as Middleton’s best prediction. “You were insistent,” he wrote. The following month, she had another dream about her parents, which she later interpreted as a warning to Barker. In the dream, Middleton was staying in a boarding house by the sea. “For a brief period, we were happy and had tea,” she recalled. Then her mother rose and climbed into a black car, pushing Middleton away. She understood the dream to indicate the passing of someone close to her. It was lunchtime, on Sunday, July 28th. “This may mean a death,” Middleton wrote to the Premonitions Bureau. “All day I have felt as if in a trance.”

Barker’s experiment closed in on him. Eighteen months after the Premonitions Bureau was launched, his two most reliable percipients had received signs that he was about to die—eliciting in him a state of mortal anticipation such as he had studied and thought about for years. When I told contemporary nocebo researchers about Barker’s work, they sensed a lure in the trap. “He wanted to know,” Ted Kaptchuk, a professor at Harvard Medical School, told me. “I work with that.” In a study that Kaptchuk led, in 2006, he found that around one in four participants reported negative symptoms in a harmless situation. “Barker’s case might be one in a hundred thousand,” he said. “And, once you get to that, you are not able to do science, you really have to just stand in awe, and say we can’t know.” In the early Middle Ages, it was a sign of a good life to sense that your death was at hand. “Know ye well,” Gawain said, “I shall not live two days.” Adler, who studied the Hmong deaths in the eighties, described the moment of a death, even of someone who is terminally ill, as a meeting point between what we know and what we never will. “It’s an asymptote,” she said. “We can get closer and closer and closer, but I am not sure we will ever have the answer.”

On August 18, 1968, Barker suffered a brain hemorrhage at home, in Yockleton. He was taken to Copthorne Hospital, in Shrewsbury, where he died. He was forty-four years old. Enoch, his closest colleague at Shelton, went to visit. “You just stood outside,” he said. “It shook me rigid.” Enoch exchanged Christmas cards with Jane, Barker’s widow, until a few years ago, when she died. I contacted one of Barker’s sons for this story, but he had been very young at the time, and was reluctant to speak. “There was kind of this myth that he worked himself to death,” he told me. On the day that the psychiatrist died, Middleton found herself awake in the early hours. She was choking and gasping for breath. She called out for help. ♦