Sini and Annie were only supposed to stay with the Oostervelds for two weeks, but in actual fact, they've stayed with them for two whole years. That's because Mr. Hannink never came back for them.
Not that anyone's complaining, of course; the girls are well-liked by Dientje, her husband, and his mother. Furthermore, the young sisters are much safer here than they were back at the Hanninks', where they hid from the Nazis for two months.
But Sini and Annie were never completely safe; there was always the danger that the Germans would find them and ship them off to a concentration camp. And now that danger has increased.
The Germans have been going around picking up men to use as forced laborers back in Germany. Dientje's husband, Johan, is worried that they'll come to his house and take him away. If they do that, then there's a very real danger that they'll search the house and discover Sini and Annie.
As things have become so dangerous, Dientje reluctantly concludes that Sini and Annie will have to be sent back to the Hanninks. Johan's mother tries to stop her, but Dientje is firm; the sisters need to be sent back to the Hanninks for their own safety.