She would not become directly involved in the Wallenberg case until October 1989, after Soviet authorities returned Wallenberg's possessions to his next-of-kin, acknowledging their “tragic mistake,” but failing to present any evidence of his death. At this point, Mesinai states, she committed herself to the task of ascertaining Wallenberg's fate “beyond reasonable doubt.” In 1991, Mesinai and Mikhail Kazachkov, a recently released Soviet prisoner, created the Ark Project, dedicated to enforcing “rule of law” in the case of foreign prisoners in the Gulag. Kazachkov and Mesinai initiated a trans-Russia appeal for information regarding missing American prisoners of war, both through publication in the human rights press and radio networking. Ark's discovery of Victor Hamilton, a former NSA cryptologist being held in a psychiatric prison hospital under another name in the Soviet Union, was world news. Because of this case and others in which she became involved, Mesinai was able to establish that anonymous foreign prisoners or dual nationals were still being held in asylums and psychiatric facilities throughout the former Soviet Union. Ark also worked with the families of American pilots lost in Cold War shoot-downs, leading to extensive media coverage through the NBC News Moscow Bureau, as well as a prize-winning article in "U.S. News & World Report", in which Mesinai spoke of the Soviets' “policy of denial.” .” In 1994, at the invitation of Wallenberg’s half-brother, Dr. Guy von Dardel, Mesinai became an ad hoc consultant to the official Swedish-Russian Working Group on Raoul Wallenberg’s Fate and instigated an archival research project to seek traces of Wallenberg in psychiatric facilities in Western Russia. As the majority of the earlier records had been removed to the East, she reverted to her comprehensive study of eyewitness reports, focusing also on other Swedes in the Gulag who could be mistaken for Wallenberg. In 1997, after assisting "U.S. News & World Report" with the reporting for a feature article, “The Angel Was A Spy,” Mesinai was employed by the Government of Sweden to do a full-time study of selected cellmates, indirect eyewitnesses and analogous cases, which might offer a paper trail that could lead back to Wallenberg. Having gained unprecedented access to numbered prisoner files in 2000, Mesinai was able to place Wallenberg in a series of six missing numbered prisoners, should he have been convicted rather than executed in 1947.