The Scarlet Pimpernel aka The Scarlet Pimpernel (Book 1)

In 1793, the terror of the French Revolution is at its height, and the guillotines are busy. But a mysterious figure is staging daring rescues, and Citizen Chauvelin, the head of the Central Committee of Surveillance, is determined to discover his true identity, and uses a number of informants, including the popular actress Minette Roland.