Even at first glance the postcard carries with it a sense of menace. There is the postage stamp of the German administration in Poland with the eagle and swastika. It, in turn, bears a stamp commemorating Nazi party day in August 1943. It is addressed to a Jew in Bucharest and there, on the left hand side of the card, is the heavy black stamp of the Romanian censor.
The visible message is innocuous enough. It is from Lola Bergman in Krakow, dated 20 August 1943, who writes in black ink in German: "My darling, I remember you with love. Lola." It is sent to Jacob Rosenblum in the Romanian capital. The only slight surprise is that at the height of the Second World War, when the slaughter of European Jews by the Nazis was under way, that the message should be so brief. But when the card is rubbed with a hot iron the faint brown lines of a second and much longer message, disjointed but frantic, become visible. It describes a concentration camp. "Death camp, the rest deceit" are the opening words. He or she speaks of the "incinerator, agonising hell, children of four and under." After the first line-and-a-half the message switches from cursive to block capitals, as if the writer feared the words would not be understood. Some, such as "Walpurgisnacht - the night of the witch-hunt", are cryptic. Others are graphic, mentioning starvation and "oat porridge" and referring to an epidemic. The writer speaks of torture, terror and "killing by gas." In a switch of topic, and speaking as if the intended reader would know those involved, the writer says somebody's "wound has healed. I was very afraid of his illness." The rest of the message gives the impression of resistance activity. The letter is signed "Otto".
It is a unique document, given to the International Centre of Holocaust Studies at Yad Vashem, the Holocaust memorial in Jerusalem, by the daughter of Theodore Feldman, who obtained it 20 years ago in Bucharest. Mr Feldman, a Hungarian Jew who lived in Romania before emigrating to Israel, survived Theresienstadt, a forced-labour camp for Jews in Czechoslovakia which the Nazis designed as a "show concentration camp" which foreign visitors could visit, to counter atrocity stories. For two months Saul Greenstein, an archivist at Yad Vashem, has pored over the documents, trying to find evidence for the existence of Lola Bergman, Jacob Rosenblum and "Otto."
Mr Greenstein did find a Lola Bergman of Krakow, a Polish Jew, mentioned on an ageing card of the International Red Cross Tracing Service. Born in 1906 she was deported to Plaszow camp, near Krakow, in 1943, then to Auschwitz and finally to Belsen. She survived, but in the turmoil at the end of the war she disappeared. The same Red Cross card shows that somebody, a friend or a relative, looked for her in 1949, but did not find her. It is more likely that the postcard refers to Plaszow, to which most Krakow Jews had been sent in 1943, than Auschwitz.
The identity of Otto, the ostensible author of the message, is equally elusive, even supposing he used his real first name. Mr Greenstein, assisted by Vagi Zoldan, who is writing his PhD on Adolf Eichmann, believes he might be Otto Haas, an Austrian social democrat and opponent of the Nazis who belonged to a resistance organisation based in Vienna.
Haas was arrested in 1942 and executed in Berlin in 1944. He was therefore in a position to know what was happening in the camps. There are two other pieces of evidence: his handwriting, of which Mr Greenstein has several examples, is similar to that on the postcard written in invisible ink. Secondly, the Haas organisation commonly placed names and places at the end of a message - on all other cards they are at the beginning - to indicate a hidden text.
Mr Greenstein says there is one simple pointer indicating that Lola Bergman knew her letter was to carry a second, secret text. Her message is very short. All other such cards he has examined are crammed with information about the flight and survival of family and friends. Lola's prosaic love letter, however, left plenty of space for Otto to tell of terrible experiences and crimes.
Visible message reads: "My darling, I remember you with love. Lola. 20 August 1943. Krakow."
The message written in invisible ink:
"DEATH CAMP, THE REST DECEIT. FROM THE NIGHT OF THE WITCH-HUNT: HUNGER,
STARVATION, DOG FOOD OAT PORRIDGE, A DOG'S LIFE, AN EPIDEMIC, TORTURE TORTURE CHAMBER, DEGRADATION, DISRESPECT VIOLENCE, INCITEMENT, TERROR, FRIGHT KILLING BY GAS, UPPER COURT (or)
GALLOWS, MURDER, INCINERATOR, AGONISING HELL. CHILDREN OF FOUR AND UNDER. A BAND OF THIEVES COLD A DECLARATION CRYING TO THE HEAVENS THE NEWSPAPER ARRIVED I HEARD IT FROM HIM THE HEAT AFFECTED HIM A LOT THE WOUND HAS HEALED. I WAS VERY AFRAID OF HIS ILLNESS. K IS FULFILLING HIS MISSION WE WILL DO WHAT WE HAVE TO.
URGENT: SIGNAL PISTOLS, CAMERA, INVISIBLE INK. URGENT: AIRBASE, CONTINUOUS LISTENING, THE TIME HAS COME
THE KETTLE HAS BOILED