Communist dictators tend to be garishly embalmed. The corpses of Lenin, Ho Chi Minh, Kim Il Sung and Mao have become tourist attractions. Some of them wanted to be cremated. Instead they were placed in ornate coffins of crystal in elaborate, dimly lit mausoleums that are the focal points of vast city squares. Expert undertakers wage a complicated battle against time to keep the dear leaders seemly for the hordes that file past the coffins to pay their respects.

The most romanticized Marxists, though, are the ones that got away, the locations of their bodies not verified for decades: Che Guevara, who was shot in the jungles of Bolivia; Patrice Lumumba, who was shot in the jungles of the Congo; Salvador Allende, who was shot (or shot himself) in the Chilean presidential palace and dumped in an unmarked grave in Valparaíso for the length of Augusto Pinochet's dictatorship. And finally there is one whose corpse remains officially missing: Rosa Luxemburg, who was also shot, in a car in Berlin, and dumped in a canal.

Luxemburg, a Polish Jew born in 1871, lived a Pan-European political existence in a time of Pan-European tumult. She was educated in Switzerland but spent most of her adulthood in Germany. She participated in the Russian Revolution of 1905 and edited and contributed to a number of leftist European newspapers of the era. Today she is most famous for her role as a leader, along with Karl Liebknecht, of the Spartacus League, a left-wing spur of the Social Democratic Party that diverged from the mainstream to maintain adamant opposition to World War I. As a result of her views, Luxemburg spent most of the war in jail, released only in 1918, when political prisoners were given amnesty.

In January 1919, after an attempted workers' revolt, German paramilitaries kidnapped Luxemburg and Liebknecht from the Adlon Hotel in Berlin. After an unsuccessful attempt to kill her by a blow to the head, Luxemburg was put in a car and shot in the head, her body thrown in the canal. When spring came, a body was fished out again. An autopsy at the city's Charité Hospital identified it as Luxemburg's, and she was buried at Friedrichsfelde Cemetery next to Liebknecht. For the next 90 years--at least the ones when the German government was not actively persecuting them--leftists came to pay their respects to Red Rosa, even though the remains in the mausoleum were said to have disappeared after Nazis desecrated the tombs in 1935. In Communist East Germany, her status was elevated to martyr, and today Berlin's Rosa-Luxemburg-Platz U-Bahn stop is at the heart of the glossy consumer district that has sprung up in Mitte since the fall of the wall. The whereabouts of her body, however, remain unknown.

In 2007, the head of Germany's Institute of Legal Medicine, Dr. Michael Tsokos, was assisting in the effort to clear out the basement of Charité Hospital, part of a process of consolidating the forensic institutes of the former East and West Germany into one building. The building that had housed the East German institute was more than a century old, and the basement was filled with macabre detritus dating back to the institute's foundation, in 1833. In the days before photographs, doctors had learned anatomy by looking at actual specimens. Hundreds of these remained--tissue samples, ears, brains. There was also a body. Headless, mummified and missing its hands and feet, it had no identification to indicate its age or identity.

But Dr. Tsokos had heard a rumor, one that the oldest employees haunting Charité would talk about from time to time: that Luxemburg's body had never actually left Charité Hospital and that some other corpse had been fished out of the canal and buried instead. Dr. Tsokos was told that someone had even claimed to have seen Luxemburg's head, which was cut off post-mortem, in a jar of formaldehyde in Hamburg the 1970s. Unfortunately, this key witness died in 2006. Undaunted, Dr. Tsokos considered the possible connection between the missing corpse with the one he had found and set out to solve a mystery 90 years old.

The story of the missing corpse is only the latest chapter in the collected mythology of Rosa Luxemburg. There's no shortage of romancing when it comes to her life: She was the subject of a 1986 biopic, Die Geduld der Rosa Luxemburg, by Margarethe von Trotta; a 2005 historical novel, Rosa, by Jonathan Rabb; and, most recently, a 2010 French musical, Rosa La Rouge. But as the introduction to a new book of her collected correspondence, The Letters of Rosa Luxemburg (Verso, 512 pages, $39.95), points out, only a quarter of her written work has thus far been available in English, the rest inaccessible to the unfortunate "Anglophone monoglot."

The new collected letters is therefore intended as a companion volume to the forthcoming 14-volume collection of her newly translated complete works. It consists of 230 letters to 46 different recipients and spans from 1891 to Jan. 11, 1919, four days before her assassination.

While certainly useful and exciting for the Anglophone monoglot scholar of Rosa Luxemburg, the epistolary Rosa Luxemburg experience can at times be slightly tedious for the casual reader--and this is only a fragment of the 2,800 letters, postcards and telegrams contained in the six-volume German edition.

As Luxemburg wrote, "It's the German thoroughness that prevents a true picture of life or of the times from being created, a picture that should be tossed off with light strokes."

The bulk of the letters in the first part of the book are addressed to Leo Jogiches, an activist who was also murdered in 1919 and was Luxemburg's lover from the 1890s to 1907. Luxemburg variously refers to Jogiches as "precious gold," "my bobo" and "my little mite." Following their protracted arguments and reconciliations via one-sided letter is rather like trying to act sympathetic toward a friend whose boyfriend you hate. "He's a controlling asshole!" you want to tell her. But then you remember that this is a woman who devoted her life to things much greater than mere boyfriends.

There is some soap-operatic satisfaction to be gleaned, however, when she recounts "a brief and soft-spoken but frightening confrontation--during a trip on an omnibus" when, after he has learned that Luxemburg has taken a new lover (the dashing physician Kostya Zetkin), Jogiches declares that he would sooner kill her than lose her. After the bus ride, Luxemburg and Jogiches meet friends at a nice restaurant.

"A fine orchestra was playing, in the gallery, music from the last scene of Carmen," she writes, "and while they were playing L softly whispered to me: I would sooner strike you dead." Yikes!

As for the momentous political developments Luxemburg lived through and her stints in and out of prison, history comes through only in fragments--"Dear Vladimir," she writes to Lenin in Dec. 18, about a month before she died. "I am taking advantage of my uncle's trip to send all of you heartfelt greetings from our family, Karl, Franz, and the others. God grant that the coming year will bring us great fulfillments."

Footnotes assist in historical orientation, but in many ways the letters serve to remind that political movements are made up of incremental bureau
cracy and banal accounting as much as soaring speeches or dramatic marches.

Her best letters, then, are those written from prison, where she was held for almost all of World War I. Here monotony and loneliness provoke a literary unity between the smallest details of her everyday life and the larger political endeavors that she has tried to accomplish. She must face the depth of her commitment, and finds she has "become as hard as polished steel and from now on will neither politically nor in personal relations make even the slightest concession."

But she is drowning in memories. A wasp flies into her cell and she writes, "It's such a reminder of summer, of the heat, and of my open balcony in Südende with the broad view out onto the fields and the groves of trees shimmering in the heat, and of Mimi [the  cat] lying in the sun all folded together like a soft package, blinking up at the buzzing wasp."

She recalls the moving shadows of tree limbs across a cafe table in Berlin, the jubilation of Karl Liebknecht on a country outing one summer, the minutia of a frozen bumblebee "cold and still as though dead, lying in the grass with its little legs drawn in and its little fur coat covered with hoarfrost." In her letters to her friends, who sent her, it seems, a near constant supply of flowers and cookies, she constantly asks them to join her in her remembrance:

"Do you remember the fabulous full-moon night in Südende," she writes, "when I was walking you home, and to us the gables of the houses, with their sharp black outlines against the background of a tender blue sky, seemed like the castles of knights of yore, do you remember?"

She describes singing an aria from Figaro to a flock of titmice on her windowsill, the blackbirds that she feeds, her advances in her botanic studies and a ladybug she has wrapped in cotton wool to protect from the frost. But as soon as one is tempted to begin thinking of her as a nice Disney character who sings to birds, she brings us horribly back to earth.

In her most powerful letter, which must also be one of the most powerful letters of the German experience of World War I, she is merely describing the regular delivery of bloodstained army uniforms that come to the prison to be cleaned and mended for reuse. On one delivery, the cart is being pulled by a yoke of undomesticated water buffaloes, spoils of war from Romania. The buffalo must be heavily beaten to obey, to the extent one's hide had split.

"The one that was bleeding kept staring into the empty space in front of him with an expression on his black face and in his soft, black eyes like an abused child," Luxemburg writes. "How far away, how irretrievably lost were the beautiful, free, tender-green fields of Romania! How differently the sun used to shine and the wind blow there, how different was the lovely song of the birds that could be heard there, or the melodious call of the herdsmen." She begins to cry. The prisoners unload the sacks of bloody uniforms while the soldier who beat the oxen paces in a corner, whistling to himself. "And the entire marvelous panorama of the war passed before my eyes."

I first read about Dr. Tsokos and the body from the basement that might be Luxemburg's corpse in the papers. After the discovery, a search ensued for sentimental tokens that might have traces of Luxemburg's DNA. A leftist member of the German parliament styled her updo in honor of Luxemburg. In a photo made public after the discovery, the corpse looked Classical in its repose, lying on white cotton drapery at the mouth of a scanner like a headless Venus de Milo, its surface the color of a used tea bag. The legs ended just below her bended knees and the upraised arms were cut off above the elbow. After 90 years in a cellar, one would expect a skeleton, but the body had served as the object of study for medical students as exemplary of a natural mummification process called adipocere that occurs in corpses that have been immersed for extended periods in an anaerobic environment--such as mud at the bottom of a canal.

In early 2010, I happened to be in Berlin wandering around Rosa-Luxemburg-Platz and I started to wonder what had happened to the corpse, so I called Dr. Tsokos and, on a frozen January day, went to the Institute of Legal Medicine to meet him. His office was located in a compound of older brick buildings arranged around snowy courtyards that were scattered with birch trees. It had the feel of a sanitarium, and I half-expected to see nuns pushing invalids around in antique wheelchairs with blankets on their laps, but the sidewalks were empty.

Dr. Tsokos was a media-savvy guy, casually dressed in a sweater and jeans and cavalier about the more chilling aspects of his life's work. His interest in the mystery corpse seemed purely technocratic--he was somebody who was obsessed with his job, and not too concerned with leftist politics. Sitting before a dark wooden cabinet filled with skulls, he proceeded to tell me of all the unsuccessful attempts that had been made to identify the corpse.

He had begun with the original autopsy report from June 1919, which was riddled with inconsistencies. It had noted no signs of head trauma, and witnesses to Luxemburg's murder had said that she had suffered a blow to the head with a rifle before her death. There was no notation of hip disease, but Luxemburg had walked with a limp from a degenerative hip disease she had as a child. The autopsied body was shorter than Luxemburg's recorded height (even though she described herself as "Lilliputian"), and, most curiously, the doctors had not followed autopsy protocol--strange, because one of them was responsible for teaching it.

"I thought, 'Oh, shit, this is really interesting,'" Dr. Tsokos said. He went to the state archive to search for a postcard with a stamp she might have licked, leaving DNA evidence. But Luxemburg had always used water to wet the adhesive. He searched for a hat or a coat that she might have worn and left a stray hair on, but he found none.

He decided that he would instead operate on the exclusion principle, and prove that the body was not hers, but every step he took seemed only to affirm that the corpse was Luxemburg's: radiocarbon dating revealed that the woman had lived at the turn of the 20th century; a CT scan of her internal organs revealed that she was 47 when she died; the body had evidence of hip degeneration and was sufficiently Lilliputian.

Dr. Tsokos sent tissue samples to Munich, where a method of identifying trace isotopes in bones revealed that the corpse had lived in Poland, Switzerland and Berlin, and that it had signs of malnutrition that corresponded with Luxemburg's extended stints in prison. He issued a public call for information and received more than 100 emails in response. Nothing came of the 10 or 20 that were actually of interest: Luxemburg had kept a herbarium as a hobby, and four of her botany books were discovered in an archive in Warsaw, but they had only male DNA on them. A grandniece was located in Israel, but since she was not a direct descendant there was only a 50 to 60 percent probability that they were related. Luxemburg never had children.

Dr. Tsokos was in a bind: He could not prove that it was her, but he could not prove that it wasn't her, either.

"For me I don't care if it's her or not her," he said. "It's just an amazing story. It's a murder case that was 90 years old. I wanted to try and ID whoever it is."

So he did what he had to do: The body was turned over to the police and buried anonymously.

ewitt@observer.com