It's WWII London. Despite being already engaged to British officer Hugh Palgrave, and despite thinking him impertinent when she first meets him, Grace Allingham, daughter of politician Sir Conrad Allingham, falls under the charms of visiting French officer, the Marquis Charles Edouard de Valhubert and agrees to marry him only after knowing each other for a few days. Their post marriage time together is equally as short as Charles is called off on active duty on day three of their honeymoon. Those three days however produce a son, Siggy - short for Sigismond. Charles' service extends past the end of the war with no leave. It isn't until nine years later that Charles' military duty is completed, when they finally see each other again and try to pick up where day three of their honeymoon left off. That is easier said than done as their relationship circumstances have changed - which includes most specifically Siggy, who has had his mother all to himself for eight years - and that they never really had to deal previously with their differing cultural mores, Charles' which includes socializing with beautiful women, Albertine being the one that bothers Grace the most. For their marriage to survive, they will have to overcome one more obstacle which they don't even know is working against them.
—Huggo