Dr. Richard Baer had just completed his medical training at the University of Illinois at Chicago when he joined a south suburban psychotherapy practice. There, in a modest office with a view of 95th Street, Baer, now 55, first encountered the patient whose treatment would, in many ways, come to shape his career. The patient, a 29-year-old woman who was referred to him for treatment of depression, began to tell him stories of horrific abuse suffered at the hands of her father and grandfather. Later in her treatment, which lasted nearly 20 years and followed Baer from the south suburbs to private practice on the North Side, she began to reveal an enormously complex inner life that included 17 different personalities.

Baer eventually decided to write about the complicated, bizarre, and often harrowing process of "reintegrating" the personas into a single, functional person through hypnosis and visualization. The patient, who has taken the pseudonym Karen Overhill, became a collaborator on the project, adding some of the letters, journal entries, and drawings created by her "alters," who included men, women, and children of varied ages and races.

The resulting book, Switching Time (Crown Publishing; $24.95), is to be out in October. It is the first story about multiple personality disorder written from the perspective of the treating physician and one of very few texts on the subject to follow a patient from diagnosis to cure.

No longer in private practice, Baer, an Oak Park native, is currently medical director for Medicare at National Government Services, a large company that assists healthcare providers in dealing with that federal system. Chicago sat down with him in his elegant Old Town townhouse to talk about the book and the complex questions it raises about therapy, truth, and the definition of self.

Q: Besides telling the story of one remarkable case, this book offers insight into the day-to-day world of psychotherapy. And a lot of it, especially your work at the start of your career, sounds pretty transactional and dull: You just keep prescribing antidepressants until they start working.
A: Different disorders require different things. This patient was referred for chronic depression. . . . She had chronic pain resulting from surgery, from delivering her daughter by cesarean section. People who have chronic pain often have depression. I knew from her manner that her depression was serious and had to be dealt with before anything else. So, really, I was just sort of wanting to move her along. . . . There are many patients, like elderly depressed patients . . . and they've lived their life and they don't really want to talk about it. So you give them medication and, in a matter of a few weeks, they're OK again. With this patient, I thought she was just a depressed woman who needed medication. Obviously, I was wrong.

Q: In the book, we start to get our first hint that something beyond regular depression is going on when Karen says, "I'm not sure if this is important, but I fainted three times at the altar when I got married." When did you begin to think that she might not be an ordinary patient?
A: Curiously, when you do a psychotherapy session, very often the patient says something very revealing and provocative when they're walking out the door, so you can't ask them about it. When she said that, I didn't know what it meant. Certainly, it was odd. There were lots of little tidbits of things that were odd. I would ask her, "How did things go yesterday?" and she wouldn't know.

Q: Karen was in therapy with you for 18 months before she began to talk to you in detail about having periods of time for which she couldn't account. And then it took another year and a half before you told her that you thought she might have a personality disorder, in addition to her depression. That seems like a long time.
A: You have to be very, very careful about suggesting things to a patient. I think these [multiple personality] patients are very, very rare because of the circumstances required to create them. It takes a significant amount of trauma to cause a person to start to disassociate from it and that trauma has to take place over a sustained period of time, bringing with it multiple disassociations that become established as "alters." . . . The history of abuse that my patient described certainly met those criteria. But you don't force things on a patient. They bring things out when they are ready.

Q: Certain elements of the abuse and trauma Karen told you she suffered seem simply too bizarre to be true.
A: Which parts?

Q: Well, do you think there really was a cult of people—led by her father and grandfather, and including a priest, a cop, and a funeral director—who were torturing and molesting kids on the Near West Side in the 1960s?
A: My thought about the "cult" stuff is that yes, in fact, it probably did happen that way. . . . My understanding is that [Karen's grandfather and father] collected these people over the years. I don't know how. Some of the women were prostitutes. And, you know, could you find a cop like that? You probably could. And a priest? Well, now we know for sure that's possible. And a teacher? Sure. . . . In anticipation of these sorts of questions, I started collecting little articles from all around and you do see these stories—a teacher here, some youth group leader there—in different places. It always seems so bizarre to normal people, and you think it can't be real.

Q: Some of it, like the police officer who regularly abused her shooting himself in the head, seems like it could be verified if true. Did you try to track some of that information down?
A: I didn't at the time. There's a problem with that from a psychotherapeutic point of view. If you try to be a detective, you're demonstrating that you don't trust the patient. The question for me was, Would it change her therapy whether it was true or not? And the answer was no. . . . But, of course, I was curious about it. . . . Later, we did try to go back and get her childhood medical records, but we couldn't get anything. The hospital only kept records going back 20 years. . . . She showed me the arrest records [the patient's father was later charged with molesting another young relative] and they were all legitimate, as far as I could see.

Q: Much of the abuse Karen describes and language you quote her as using to describe it, including the terms "ritual abuse," "Midnight Host," and "Black Masses," seems reminiscent of the repressed memory cases of the 1980s that were later proven to be false. Did you worry that her memories of abuse had somehow been implanted or created?
A: It's impossible to know for sure. There are a couple of alternatives: She could have read about and incorporated those stories into her memories of being hurt. . . . The other possibility is there is a network of people who do this to have a group experience of hurting children in some way. Not a real cult, necessarily, in the sense of a large, formal organization, but some sort of made-up group.

Q: Ultimately, does the truth of it matter—or only her belief that it all happened to her?
A: Again, I'm curious. . . . But one of the nice things about psychotherapy is that you don't have to decide right away if it's true or not. I will say that she was completely consistent in all her memories, in all the alters, over ten years. . . . And the other thing that convinced me was that she was never melodramatic about it. She was very matter-of-fact. . . . She never gave me any reason to doubt her. So the conclusion I came to was that it did happen. I think it was a stupid, made-up cult, led by the grandfather.

Q: The different personas, created as a kind of coping mechanism for dealing with incredible pain and trauma, were seemingly somewhat aware of each other, but did not necessarily share memories or experiences. And they had different handwriting, different medical conditions, even different vision, with some needing glasses and some not. From a medical point of view, how is this possible?
A: That's one of the things that, if one was a researcher and wanted to study this kind of phenomena, you could put her under examination and try to figure out. But that wasn't my role. . . . My focus was always on how to be her psychotherapist.

Q: One of her alternate personalities, Holdon, sometimes guided you on how best to treat her disorder. That must have seemed slightly bizarre.
A: Yes, in a sense. In the medical literature, they talk about a gradual integration of the alters and them sharing time with each other. We attempted to do that, to have multiple alters "out" at once, but she found it exhausting. She couldn't handle it. So Holdon came up with this plan. . . . He had a memo and it was step by step by step how to do it: which alter to merge and in what order. It was a little spooky, but you are just talking to someone, so it's not like their brain is going to explode if you get it wrong. Obviously, I didn't want to do any harm, but it seemed worth trying.

Q: I was struck by Karen's admission that she would read, watch TV, and listen to music all at once, with different alters absorbing each thing. Surely her family and friends must have found that a little odd. How much do you think they knew about her mental state?
A: I don't think her children knew. She said that her husband could get her to switch. Now, he didn't know that her different personas had names, or anything like that, but he knew that sometimes she was much more accommodating than others. . . . So he would get up in her face and yell and one of the more docile alters would come out to placate him.

Q: During the time she was seeing you, Karen was raising her children. Given her propensity to lose time, were you ever concerned for their safety?
A: It's not much in the book, but she talked about her children and parenting all the time. There were parts of her that were very responsible, Katherine and Holdon, and they were used to managing her children. . . . The parts of her that were children would come out to play with them. If you think about it, it's not so far afield from what other people do, that there's a more childlike part of your personality that comes out when you're down on the floor playing with a child and a more adult part that comes out when you're working. In her case, though, it was just a much more distinct split. . . . The kids didn't really know anything different and I think that's just how they thought Mom was, with different moods and manners.

Q: Many psychiatrists say there is no empirical evidence to support the idea that multiple personality disorder even exists. How do you answer that?
A: I think it's pretty clear that there are documented cases and there have been for a long time. In the eighties and nineties it became a fad, just like for a period of time everyone was codependent and addicted, and so, a certain level of therapist used this to understand everything. . . . In some of the recent books, where there is no particular history of chronic abuse and the different parts have no particular role to play, the disorder makes no sense to me. This system [as Karen referred to her collection of alters] was an exquisitely crafted coping mechanism: Different alters were created to deal with different situations and each performed his or her role.

Q: At some point in Karen's treatment, you had to start thinking that there might be some professional glory in it for you. How does a good therapist deal with that kind of excitement?
A: I did have a private thought and my private thought was, "This is a great story." And I had the thought of, How could I tell this story, how could I tell it as good as I was getting it? So I felt a strong urge to want to replicate that for people, but didn't know how I would ever do that.

Q: Is Karen making any money from the book, which, after all, includes not only her story, but her letters, journal entries, and drawings?
A: She benefits from the book.

Q: Her therapy ended June 30, 2006. Have you been in touch since then?
A: We talk on the phone. We visit from time to time.

Q: While writing this book, you actually earned a master's degree in creative nonfiction at Northwestern. Do you have plans to write another?
A: Yes. . . . I think what I was good at in psychotherapy was explaining to people how they develop patterns in their relationships. . . . So I would like to write something about that. Not a self-help book, but sort of a self-explanation book.