On 5 July 1942, Anne's older sister Margot received an official summons to report to a Nazi work camp in Germany, and on 6 July, Margot and Anne went into hiding with their parents Otto and Edith. They were later joined by Hermann van Pels, Otto's business partner, including his wife Auguste and their teenage son Peter. Their hiding place was in the sealed-off upper rooms of the annex at the back of Otto's company building in Amsterdam. Otto Frank started his business, named Opekta, in 1933. He was licensed to manufacture and sell pectin, a substance used to make jam. He stopped running his business while in hiding. But once he returned, he found his employees running it. The rooms that everyone hid in were concealed behind a movable bookcase in the same building as Opekta. Mrs. van Pels's dentist, Fritz Pfeffer, joined them four months later. In the published version, names were changed: The van Pelses are known as the Van Daans, and Fritz Pfeffer as Albert Dussel. With the assistance of a group of Otto Frank's trusted colleagues, they remained hidden for two years and one month.