Actually, the sergeant in Bridewell prison asks two favors of Isabel.  First, he asks that Isabel share the food scraps that she has brought only for Curzon.  Isabel agrees to this, and the scrap bucket is passed around to everyone.  The sergeant is impressed that the scrap bucket still has some food in it when it makes it back to the sergeant the first time.  As a result, the sergeant commends the soldiers for taking only what they need.  Second, the sergeant asks Isabel to carry notes to the regiment's captain.  Isabel refuses to do this particular favor because her trust of the rebels has been diminished.  Isabel is unable to be free due to her slavery; therefore, Isabel does not want to have much to do with the fight for freedom from the British.