What crisis occurs in Act 1, scene 5 of "The Diary of Anne Frank"?

In Act 1, scene 5, the Franks and the Van Daans are celebrating Hanukkah. They are having a good time, and Anne makes them all laugh when she wears her lampshade hat. There is a brief quarrel over the cat, and Mr. Van Daan orders Peter to get rid of it. But the situation calms down when Anne begins to sing, and they light the Hanukkah candles. Mr. Frank begins to blow out the candles, and Anne complains that they are supposed to be left to burn themselves out. Mr. Frank tells her God will understand that they need to conserve their candles.

Suddenly, there is a loud crashing noise from downstairs, and the group in the attic are terrified. They wonder whether the Green Police or the Gestapo have discovered their hiding place and have come to get them. Mr. Frank quietly slips downstairs to find out what happened. When he comes back, he tells the others that it was only a thief and that he is gone. They are very thankful and continue their celebration, singing songs in praise of God.