The year is 1623, the place Haarlem in the Netherlands. Diogenes - the first Sir Percy Blakeney, the Scarlet Pimpernel's ancestor - and his friends Pythagoras and Socrates defend justice and the royalist cause. The famous artist Frans Hals also makes an appearance in this historical adventure. Orczy maintains that Hal's celebrated portrait of The Laughing Cavalier is actually a portrayal of the Scarlet Pimpernel's ancestor.