On Tuesday, Flatiron Books released Twin Peaks: The Final Dossier, a companion book to the series (both the original run and Showtime's revival) written by Twin Peaks co-creator Mark Frost. It's Frost's second novel tied to The Return, after last year's The Secret History of Twin Peaks. The books help fill in the backstory and demystify some of the show's impenetrable mythology (Frost is more generous with explanations than his co-creator David Lynch).

Like The Secret History, The Final Dossier takes the form of a case report by FBI Field Agent and Blue Rose Task Force junior member Tamara Preston, played by Chrysta Bell on the show. She found out a lot about characters from the original series who were missing in The Return, discovered some half-clarifying, half-murkifying information about what we saw in both editions of the show, and presents some theories that seem to explain some things while leaving Frost some plausible deniability about whether they're actually what happened.

Here are the biggest revelations.

Kyle MacLachlan and Sheryl Lee, <em>Twin Peaks</em>Kyle MacLachlan and Sheryl Lee, Twin Peaks

1. Leo Johnson (Eric Da Re) died in 1989. Shelly's (Madchen Amick) husband was last seen in the original series when Windom Earle (Kenneth Welsh) left him tied up with a basket of tarantulas over his head that would fall if he let go of the string between his teeth. At some point soon after that, Earle came back and shot Leo five times in the heart, leaving Shelly free to openly have a relationship with Bobby Briggs (Dana Ashbrook). They married a year after Leo's death. They didn't stay married, but still; Shelly and Bobby were two of the lucky ones.

2. We know what happened to Donna. In the original series, Donna Hayward (Lara Flynn Boyle) was Laura Palmer's (Sheryl Lee) best friend. She was absent from The Return, and now we know why. Soon after she graduated from high school, she moved to New York, cut off contact with almost everyone from Twin Peaks and became a very successful fashion model in the '90s. But she descended into addiction and went to rehab five times, and her venture capitalist husband divorced her after the last one. She then moved to Middlebury, Vermont to live with her father, who had divorced Donna's mother and moved across the country to start over. She's still sober and is studying to be a nurse practitioner. It turns out Donna, too, is one of the lucky ones.

3. Donna's sister Gersten (Alicia Witt) wasn't so lucky. Gersten, the Haywards' youngest daughter, had a genius-level IQ but a fragile constitution. She went to Stanford when she was just 16, but she had a nervous breakdown in her second semester and went back to Twin Peaks. She never really recovered. Like her sister, she descended into addiction, which is how she got involved with Steven Burnett (Caleb Landry Jones), the drug dealer who was married to Shelly and Bobby's daughter Becky (Amanda Seyfried). Gersten and Steven have both been missing since their bizarre scene in the woods in "Part 15."

4. Audrey (Sherilyn Fenn) had a weird quarter-century. A dark fan theory is indeed true, and Evil Cooper (Kyle MacLachlan) — referred to in the dossier as "the Double" — raped Audrey while she was comatose in the hospital recovering from her injuries sustained during the bank vault blast, which resulted in Richard's (Eamon Farren) birth. She cut herself off from her father's money and put herself through community college, and eventually opened her own beauty salon. When Richard was 10, she married her accountant, Charlie (Clark Middleton), for "financial convenience," as Agent Preston puts it, and as we saw on the show, it's an unhappy marriage. Four years ago, she closed the salon and vanished from public life into "either agoraphobic seclusion, or — one troubling rumor suggests — a private care facility." So maybe her dance in "Part 16" was all a fantasy.

Sherilyn Fenn, <em>Twin Peaks</em>Sherilyn Fenn, Twin Peaks

5. What happened to Annie (Heather Graham) will break your heart. Annie Blackburn had a hard life before she got to Twin Peaks. The only time she was ever happy was during her time in Twin Peaks with her half-sister Norma (Peggy Lipton) and her boyfriend Agent Cooper. But then Windom Earle took her to the Black Lodge, and Cooper went in to save her. She made it out, but the Double came back with her instead. She's been catatonic — almost like her consciousness has gone completely internal — since the morning after she came back, with a few notable exceptions. She tried to kill herself on the first anniversary of her return from the Black Lodge. The next morning — the anniversary of her time going catatonic — she spoke for the first time in a year, saying, unbidden, "I'm fine." And every year since then, at 8:38am on the anniversary of the day after her return, she says "I'm fine." No one around her knows why, but we do: she's answering the Double's mocking question from the last scene of the original series: "How's Annie?"

6. We learned how Dr. Jacoby (Russ Tamblyn) became Dr. Amp. After what transpired in Twin Peaks, Dr. Jacoby lost his medical license and went back to Hawaii, where he grew up. He continued to have weird, spiritual-seeking adventures, and found his way into radical politics after experiences in Florida in 2000 and New York City in 2001. He saw 9/11 as an act of karma, and the world was entering a dark age called "Kali Yuga." So he devoted himself to spreading the word about his dark age theory and how to overcome it, developing the Dr. Amp persona and building a modest but dedicated online following. One of his disciples is his former patient Nadine Hurley (Wendy Robie), and his program of "shoveling oneself out of the s---" helped her more than any psychiatric care ever did. They might be dating after they reunited by chance and Nadine told her husband Big Ed (Everett McGill) that he should be with Norma (Big Ed and Norma did get married, by the way).

7. Hawk (Michael Horse) got the Log Lady's (Catherine Coulson) log after she died. The dossier contains a report on Margaret Lanterman's funeral, and it contains a message that she gave to Hawk the day before she died. I will not reproduce it here, but it's a beautiful meditation on how "darkness will always yield to light, when the light is strong."

8. Harry Truman (Michael Ontkean) is indeed very sick with cancer. He barely told anyone in town, and brought in his brother Frank (Robert Forster) to take over for him. He's living in Seattle undergoing treatment. He never gave up looking for Cooper, though.

9. The Major Briggs (Don S. Davis) story is still fishy. The mystery of Major Garland Briggs drove much of The Return's plot, and the dossier clarifies some of what happened to him. Preston suspects that when the Double visited Briggs at his home shortly after he came back, Briggs knew it wasn't the real Cooper, so he stripped his classified Blue Rose station up in the mountains to keep valuable information from falling into the Double's hands and then faked his own death. He then entered a "metaphysical dimension" until he was contacted by Bill Hastings (Matthew Lillard) and Ruth Davenport (Mary Stofle). He came back through the Buckhorn portal, gave them his own dossier and instructed them to find the mysterious coordinates Preston suspects he stashed in plain sight somewhere. When they came back to deliver them to him in corporeal form, they were attacked by woodsmen, who killed the Major and Davenport. We still don't really know why any of this happened, though.

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10. The Double was a criminal billionaire. Cooper's evil doppelganger spent his 25 years on Earth secretly building the world's most secretive and powerful criminal empire. He used all the profits to fund his research into...whatever horrible thing he was looking for.

11. The Double might be "The Dweller on the Threshold." Preston floats a theory that the Double isn't actually a tulpa but is the literal embodiment of a different spiritual concept where a person has to confront a "Dweller on the Threshold" — "a sum total of all the dark, negative, unresolved qualities that resolve in every human being" — before crossing over into enlightenment. As Hawk said when explaining the concept to Cooper in the original series, "if you confront the Black Lodge with imperfect courage, it will utterly annihilate your soul." Cooper didn't get it right the first time, but the second time he did. Or, perhaps it was a doppelgänger possessed by the evil spirit of BOB. Preston doesn't know for sure.

12. We still don't understand Phillip Jeffries, but we're closer. The Jeffries stuff is brain-warpingly complicated, so bear with me. When Agent Phillip Jeffries (David Bowie) disappeared, he probably entered the same kind of alternate dimension outside of time and space that ageless Major Briggs did, and that Cooper did, too, later on. But we'll get to that. The Double visited Phillip Jeffries — who had taken the form of some sort of teapot living in a motel that doesn't actually exist — and asked about the coordinates and Judy. When Phillip Jeffries appeared in the FBI's Philadelphia office in 1989, he said "we're not going to talk about Judy," acted suspicious of Agent Cooper and was confused about when it was. Preston posits that wherever Jeffries has been is outside of time, so he doesn't realize that he went to Philadelphia long before the Double came to talk to him about Judy. He's disoriented about when things are. Just like Cooper was in the final scene of The Return when he asked "what year is this?"

We still don't know what's the deal with the teapot.

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13. It's Joudy, not Judy or Jowday. When Jeffries disappeared from Buenos Aires in 1987, he was investigating a case in which a major player seemed to be named "Judy." But when Preston visited his hotel room in search of clues about what happened to him, she found a word carved into the wall: "Joudy."

"Joudy, it turns out, is also the name of an ancient entity in Sumerian mythology," Preston writes. Joudy, the female form, and Ba'al, the male form, were wandering demons that fed on human suffering. Sound familiar? Apparently, when Joudy and Ba'al came together on Earth, "the resulting 'marriage' would create something more perilous." Christians and Muslims may know Ba'al by another name: Beelzebub. But residents of Twin Peaks might know him as BOB. Which brings us to the next revelation.

14. Sarah Palmer (Grace Zabriskie) is Joudy. Sarah Judith Palmer, née Novack, became a vessel for Joudy when a moth with the legs of a frog crawled inside of her mouth when she was a girl living in New Mexico. We didn't know that was what we were seeing in "Part 8," but Preston describes a record of an incident in Sarah's youth where her parents found her unresponsive in her bedroom after she heard a strange radio broadcast that caused other people who heard it to pass out, too. So both of Laura Palmer's parents were possessed by evil demonic entities.

15. Laura Palmer didn't die. That sequence of Laura Palmer's plastic-wrapped body disappearing from the beach after she met Agent Cooper in the woods the night she died? That was real. Preston went back and read newspaper reports about Agent Cooper's first disappearance, and in those stories, she found that Laura Palmer also disappeared. The night she died, or at least the night Preston had been told she died, she vanished without a trace. There was nothing about her murder in the paper. When she talked to Twin Peaks residents about it, they were uncomfortable. They couldn't remember. It was as if their brains were foggy. So there are two timelines: one where Laura Palmer was murdered, and one where Agent Cooper took her with him into an alternate dimension.

16. Mark Frost really doesn't get enough credit for what he brings to Twin Peaks. David Lynch is the face of Twin Peaks, and as the director, the show's visual surrealism and dream logic is clearly his. But The Secret History of Twin Peaks and The Final Dossier indicate that much of the story comes from him. Reading the books I get a sense that Frost does much of the plotting and myth-making, and then Lynch puts it through the Lynchifier. I don't know that for certain, but Frost going through the trouble of filling in all this backstory certainly makes me think he's more the writer of the pair. Frost's love for the characters and the world is evident, and the warmth with which he writes about certain characters — the Log Lady, Sheriff Truman, even Donna Hayward — is moving. As a fan of the show, I'm grateful that he doesn't want us to pull our hair out for another 25 years and has given us this final gift.

Or is it?

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