Phoebe is delighted to go to Brussels as companion to Sally, rather than be an unpaid governess to her sister Jane's children. Her hopes are dashed when Zachary, Earl of Wrekin, claims Phoebe is too young for the task, and refuses to escort her.
She finds herself unable to control the rebellious Sally, who gets into many scrapes even before they leave London. However, when Phoebe rescues Sally from a calamitous action, Zachary relents. But Jane's husband and his unpleasant sisters cause irritation on the journey.
Then Napoleon escapes from Elba and everything is in turmoil for Phoebe.