The Dauphin is being held prisoner by the Republicans. When he is captured by a masked intruder, Robespierre orders Chauvelin to find the boy before news gets out.

More adventures with Sir Percy Blakeney and his crew as he uses ingenious disguises and tricks to rescue French aristocrats from the guillotine, and escape the cluthes of Robespierre. And a new challenge for Percy - Margueritte has died in childbirth leaving him with a baby daughter to look after.

When brilliant French scientist, Antoine Picard, is coerced into producing a revolutionary bomb for Citizen Robespierre, only the Scarlet Pimpernel, aided by Picard's beautiful sister Francoise, can rescue him from the guillotine.