This was the best one so far I think. Flora, or Poppy as we now know her, has run to save her sister from a wrongful murder charge, leaving Kate and Caro with no explanation. The Duke of Langham happens to bump into her at the train station, and the rest is, as they say, history.
Langham is on his way home for his grandmother's birthday, where he will need to field the affections of many eligible ladies, and Poppy just wants to save her sister....which may be much easier with the help of a Duke. It's decided that they will help each other - a fake engagement to save him from his grandmother's ladies, and is help in clearing her sister's name.
Everything becomes more complicated as they're forced into closer situations, and their fake engagement begins to lead to some very real realizations and feelings. Langham begins to think that marrying Poppy wouldn't be so very bad, and Poppy is feeling a lot more than friendship for him. As they get closer to discovering the murderer, Poppy finds herself captured by him, hoping her friends will find her in time!