What fears about the Revolution does Marguerite have? What does Armand do that indicates he may have the same apprehensions?

Marguerite's biggest fear is that her brother will be killed. In Chapter Ten, the letter written by Armand and conveniently in the hands of the Chauvelin was proof of Armand's treason and an opening for the man to blackmail Marguerite.

"That letter shows him to be not only in sympathy with the enemies of France, but actually a helper, if not a member, of the League of the Scarlet Pimpernel."