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In 1979, Ruth Montgomery published Strangers Among Us, a collection of accounts of walk-ins. She included prominent historical figures among her subjects, such as Thomas Jefferson as having hosted walk-in spirits who wrote the Declaration of Independence.
Subsequently, a belief system grew up around the walk-in. It included New Age attributes such as the concept of ascending into higher frequencies of evolution, a variety of psi powers, traditional "predictions regarding Earth Changes" first cited in the Bible (Book of Daniel and the Book of Revelation) but popularized by Edgar Cayce, and predictions of dire fates for those whose vibrational levels remain unraised. In the late 1980s and early 1990s a channelling team known as "Savizar and Silarra" (Extraterrestrial Earth Mission), emphasised their walk-in status, claiming successive walk-in experiences together with corresponding name changes. The New Age walk-in belief system now includes a number of variant experiences such as channeling, telepathic contact with extraterrestrial intelligences, or soul merging, where the original soul is said to remain present, coexisting or integrating with the new one. As of 2006, an increasing number of people claim some type of walk-in experience. Walk-ins were featured on the June 4, 1999 segment of the Unsolved Mysteries television series. According to information presented on this programme, there are walk-in conventions, one of them drawing approximately 500 people.
Experiences such as those described in this article are not regarded favorably by some religious groups and mental health professionals. Some fundamentalist Christians denounce the walk-in idea as being connected with the occult. Some psychiatrists such as Herbert Spiegel and cultural analysts such as Joan Acocella believe that all of these experiences, from traditional walk-ins to the New Age variety up to and including cooperative 'healthy multiples', are mere attention-seeking playacting, or at best a "metaphor of distress" to express something the client feels is wrong, or somehow different from usual, but is having trouble describing.
Walk-ins in popular culture 
The film Here Comes Mr. Jordan, and its sequels and remakes, are a take-off on the older, spiritualist version of the walk-in concept, although the term is never used. Heaven Can Wait, a 1978 remake of Here Comes Mr. Jordan, was also the inspiration for the television series Quantum Leap, in which Dr. Sam Beckett, involved in a time travel experiment gone awry, "leaps" into events that occurred during his lifetime, displacing another person. (Although most other characters perceive Sam as the person he replaced, this is not a true "walk-in", since his body is also involved.) In an attempt to return to his own time, he needs to change the future outcome of a situation for the better, after which he can make another leap. Beckett believes that his leaps are controlled by God or a God-like force.
Hawkgirl comics, the K-PAX series of books and films, and the Twilight Zone episode "The Last Rites of Jeff Myrtlebank" have all featured situations similar or identical to walk-in experiences, although the term "walk-in" is not used.
After the Death of Superman story cycle, a handful of new superheroes appeared, among them John Henry Irons, who called himself the "Man of Steel". He never claimed to be the real Superman, but Lois Lane speculated that if Superman were really dead, perhaps his soul had moved into Irons' body as a walk-in, and she used that word.
The term "Walk-ins" was used several times in The X-Files television series. In the episode ("Red Museum") of the second season, it was used to describe the believers of a fictional cult that believed in soul transference in which enlightened spirits take possession of other people's bodies. In another episode ("Closure") of the seventh season, it was used to describe the spirits of dead children who come to convert living children from matter to energy (starlight) in order to save them from a horrible fate in life.
The TV series Ghost Whisperer (featuring Jennifer Love Hewitt) in the late 2000s used a term "step-in" when one character died, but whose soul came back into an accident victim (season 4, episode 7, "Threshold").
Stephen King's The Dark Tower series of books, specifically Song of Susannah, featured characters known as "walk-ins". In these books, parallel universes are connected through "doorways" between worlds. These are actual doors created by magical means between parallel dimensions. "Walk-ins" are human or non-human beings who appear to have accidentally stumbled through to "our" world. They sometimes do not speak English, and sometimes speak languages unidentifiable to academics in "our" world. They often appear disoriented, confused, very ill, or suffering from severe physical defects.
In the cartoon series Danny Phantom, is about a boy who gains "ghost powers" by becoming half ghost. One of them is the ability to walk-in into other people, and sometimes ghosts, to control them temporarily. On the show this is referred to as "overshadowing" someone.
A similar "walk-in" concept, and variations thereof, was used by H.P. Lovecraft in several of his short stories. A good example of this can be found in the short story "Through the Gates of the Silver Key." In this story a man returns to earth in the body of an alien being. Other Lovecraftian tales portray a more conventional walk-in idea in which an alien being comes to earth and takes over the consciousness of a human. These tales are notable because the time frame in which they were written predates the above examples by many years. Lovecraft published his short stories in the early 1900s.
See also 
- Montgomery, Ruth, Strangers Among Us (Fawcett, 1984).
- Finney, Dee, What Is A Walk-In And What Do They Do?, Greatdreams.com, retrieved 2008-01-08