Ruth Montgomery has led an interesting life. In 1936, as a young reporter for the Detroit Times, she posed as a member of a racist group called the "Black Legion" to solve a murder that had baffled the police. Montgomery not only solved the murder but uncovered the fact that Detroit's chief of police was a secret member of the organization. Later she was the first woman journalist to be featured on the popular NBC radio show "The Big Story." But her biggest "Big Story" lay ahead.

Montgomery's middle years in the newspaper profession were a steady climb up the ladder of scoops and exclusives. She once hid under a waiter's table to get into Doris Duke's honeymoon suite for an interview. Her stories filed from Havana in 1947 reportedly changed Cuban national politics of that time. The only woman reporter allowed to cover FDR's funeral at the White House, she was elected president of the Women's National Press Club in Washington in 1950 and by the time she was through writing a column for the Times-Herald called "Wash., D.C.," it would not be inaccurate to say that Montgomery pretty much had covered the world . . . on one level, that is.

Then, in the 1960s, Montgomery was introduced to the then-unknown Washington seer, Jeane Dixon. Fascinated by her story, Montgomery wrote the phenomenally successful "A Gift of Prophecy," which placed Dixon irrevocably in the public eye and launched Montgomery upon an investigation into the world of psychic phenomena, a subject that has held her attention ever since.

If one were to take a tour down the dark, fraud-filled corridors of the occult, paranormal and supernatural, one could do worse than hire Montgomery as a guide. She now has written eight books on the subject and is hailed on the dust jacket of her latest book as "America's leading authority on psychic phenomena," which probably is true.

In Montgomery's "Search For the Truth" (the title of an early book in this series) her discoveries about life, death, reincarnation and the psychic powers both of herself and others, ring truthful, if not true. But her latest book, "Threshold to Tomorrow," rings like a bell without a clapper and I can't shake the feeling that Montgomery has crossed one threshold too many.

"If you have not already met a Walk-in," begins Montgomery in the foreword, "you soon will. They are everywhere . . ." The Walk-ins are here, she explains, to help the world prepare for a shift upon its axis that will take place at the close of this century, possibly after a devastating war.

Anwar Sadat was a Walk-in. Chuck Colson is one, too. (It happened in the driveway when he begged God to "take me" as the Watergate crisis reached a peak.) Moses, Ben Franklin, Gandhi and Jesus (who Montgomery says was the greatest Walk-in ever) also are Walk-ins, or "idealistic but not perfected souls, who, through spiritual growth in previous incarnations, have earned the right to take over unwanted bodies, if their overriding goal is to help mankind."

This thought, for those of you who have not read "Strangers Among Us," Montgomery's first book on Walk-ins, may be quite a lot to swallow. But in fairness to Montgomery, it does not do to read her books out of sequence. As she evolves, so do her books, gaining weight in minds that already have been prepared by Montgomery to accept what she might have rejected herself.

There is, for instance, the matter of her "Guides," or discarnate spirits, who have been aiding Montgomery rather significantly in her writing since 1960 by guiding her fingers (after a period of meditation when she is in the alpha state) across the typewriter. Montgomery's Guides, she explains are "souls, like ourselves, who have lived innumerable earth lives but are currently in the spirit plane, as you and I will be when we eventually pass through the door called death."

The Guides' purpose is to "awake us earthlings" to the realities of the world beyond our five senses, and one cannot read Montgomery's psychic books without accepting the Guides as an empirically solid fact in her life. This reader has no problem with them. They seem to make good sense most of the time and sometimes they are quite funny.

In "Strangers Among Us" Montgomery asked her Guides if she was a Walk-in. ". . . my unseen pen pals are not given to flattery. 'No, you are not a Walk-in,' they bluntly replied . . . 'But one day you may decide to make way for a Walk-in. Until then, do that which you came into this earth to do. We'll help."

"Threshold to Tomorrow" is divided into life stories of living Walk-ins, currently occupying the bodies of human beings, most of whom suffered a traumatic or near-death experience that caused them to give up on life. They are starting New Age communes, engaged in scientific research, devoting their lives to philanthropy or still searching for their mission. But all of them are radically different people from what they were before they were "replaced" by the souls that currently motivate their activities. Regrettably, a good many of them were so unfamiliar to their spouses that they wound up getting divorced as a result.

Only one Walk-in, says Montgomery, is the "returned soul of a world-famous genius of the immediate past": Bjorn Ortenheim, a scientist-inventor from Sweden, actually is Albert Einstein. Hastening to assure us that she was skeptical of her Guides' confirmation of this fact, Montgomery says that Ortenheim has been written up in a number of respectable magazines for his alternative energy systems work, received many grants, awards and letters of praise.

If, as Montgomery maintains, we are in for it, in an apocalyptic sense, she has provided a kind of service by naming names of Walk-ins who may lead us out of the mess. But if it is not practical to move to Seattle, where there seem to be quite a number of Walk-ins (she gives names and addresses of some of them), what are we supposed to do?

Thoreau once advised Emerson on how to choose healthy, tree-producing acorns from a handful of acorns. When floated in a bucket of water, the good acorns will sink. "Threshold to Tomorrow"--compared with previous Montgomery books--floats.