"Suspicious men not familiar with the password began coming to the clinic, asking for help. There were more random searches. Then, on July 31, the German secret police suddenly appeared at the Brussels home of Philippe Baucq and arrested him. Louise Thuliez, who had been staying with the Baucq family for the night, was also arrested. Over the next five days, 35 people involved in the escape network were taken into German custody.
Prince Reginald de Croy managed to get word to those not yet arrested, including Edith Cavell, urging them to go into hiding. Edith, who didn't think she had a chance of escape, chose instead to wait for the inevitable while destroying any letters that might incriminate her or anyone else.
On the afternoon of August 5, officers from the German secret police -- Pinkhoff and Mayer -- arrived at the clinic..."
From "Edith Cavell: Patriotism is Not Enough" from Women Heroes of World War I: 16 Remarkable Resisters, Soldiers, Spies, and Medics.