We know that Lennon was murdered by a deranged former fan and have seen the footage of Lennon inviting a homeless guy in for lunch while working on the Imagine album. In her book Loving John, May Pang documents other such encounters, including this one:

There were certain of John's fans whom John referred to as "the weird ones," fans who *insisted* on seeing him face-to-face. There had been one in particular, whom I'll call "Steven," who had sent a number of telegrams from a mental hospital
somewhere in the Southwest, insisting that he could be "cured" only by looking into John's eyes. Dan [Richter, Yoko's assistant and drug-supplier] had predicted that one day Steven would turn up at the gate. Sure enough, as soon as he had been
discharged from the hospital , Steven found his way to Tittenhurst Park and camped out to wait for John. John did not want to see him. "I don't want anyone to believe that I can cure him. I'm John. That's all I am, John," he said, and he took refuge
in his house. The police kept removing Steven from the road, but no matter where they dropped him, he found his way back to the house and would not leave. He had been there for days.

"I don't know what to do about him," John told Dan. "I don't want him hurt, but I do want him to go away."

Dan tried to convince John that the only way to get rid of Steven was indeed to look into his eyes. John became more upset. Dan kept after him, and finally, after much discussion, John acquiesced. Then Dan got the idea of filming the meeting for
the Imagine film. John balked again. He did not want Steven to be exploited. Dan persuaded John that since the film was to be a photographic document of his life -- and that this was a rather strange moment in his life -- it would be permissible to
film the meeting. They could decide later whether to use the footage in the finished film.

On the appointed afternoon, with the film crew poised, John went to the gate. Steven walked toward John and slowly stared into his eyes, and John looked back. Steven was speechless. He had trouble believing that his dream had come true. He
searched for something to say but was too overwhelmed to speak. He continued to stare at John for a long, long time. Then, with tears in his eyes, he turned and walked slowly down the road. He was never seen again. Dan, the crew, and John realized
that John had "cured" Steven. John turned and walked back to the house. He was shaken by this incident, and the startling image of the "cure" continued to haunt everybody else."

-- May Pang, in Loving John

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