The warehouse workers must not notice anything
‘During the day we always have to walk quietly and speak softly, the people in the warehouse mustn’t hear us.’, Anne wrote in her diary (Anne Frank, B-Version, 11 July, 1942). They could, for example, not flush the toilet too often, because the water discharge from the Secret Annex ran along the storeroom. The sound might arouse suspicion.
Out of all the warehouse staff, only Johan Voskuijl was aware of the presence of the people in hiding. He was the warehouse manager as well as the father of Bep, who worked in the office and was one of the helpers. Johan was important to them because he could keep an eye on the other warehouse workers to see if they noticed anything. This went well until Johan fell ill in 1943 and was replaced by Willem van Maaren.
That was a major setback, because Van Maaren was curious, and he noticed that people had been in the building after closing time. The helpers and people in hiding did not trust him. Victor Kugler believed he placed small pieces of wood and other items in the warehouse, in such a way that in the morning he could see if anyone had been there.
Immediately after the war, Willem van Maaren was the only suspect in the investigation into the raid of the Secret Annex by the Sicherheitsdienst. He vehemently denied any involvement and said that Victor Kugler had known about the pieces of wood and other things. Evidence of his involvement was never found.