This exciting books is filled with conflicts between characters and caused by tense situations. The most obvious one that I can think of is the conflict that exists between Marguerite and the conniving Chauvelin, who manipulates her into agreeing to betray the Scarlet Pimpernel in order to save her brother's life. She is completely conflicted about her role in this betrayal, and goes back and forth on whether or not she will follow through. At the party where she is supposed to find the identity of the Scarlet Pimpernel and reveal it to Chauvelin, it ends up being that she doesn't have to; he never shows. But, their conflict does not end. He wants her to continue to try; he continues to dangle her brother's safety over her head. In the end, the conflict is resolved as the Pimpernel, and her brother, end up safe.
Another conflict exists between Marguerite and the escaped French aristocrat, the Comtesse de Tournay, who has taken refuge in England. The Comtesse detests Marguerite for her supposed role in the betrayal of another royal family; when these two ladies chance across each other at an inn, the Comtesse refuses to speak to Marguerite, and forbids her daughter, Suzanne from speaking to her either. That conflict never really resolves itself, but Suzanne is helped by Marguerite as Marguerite helps Lord Tony, Suzanne's crush.
So it is not only England and France that have the conflict in the novel, or husband and wife. There are conflicts between many other characters, which makes the read that much more engaging and entertaining. I hope that helped; good luck!