Charlie Simpkins, a youth living in London during the year of the plague 1665, saves a wealthy toff who is being robbed by a gang of ruffians. Charlie's reward, a golden guinea, is beyond his wildest dreams and promises all kinds of good things. Unfortunately Charlie discovers that wealth alone does not guarantee happiness or security and, together with his younger sister, he is set on a journey that will put them both in great danger. Finding himself the target of murderous criminals, Charlie attepts to leave the plague-ridden city only to discover many obstacles barring his way.