Here's an example outline for another book in the Simon and Katherine series.
It's rough, but should demonstrate the way the outline works.
Working title Simon's Dilemma. (need a better one.)
chapter 1 wedding. They use the banns so Aunt Anne-Marie and Sir Reginald et al can attend. Anne-Marie warns Katherine about married life while the Reverend makes another attempt at getting Simon to be a vicar. He explains a little of his history and reasons. Make sure the church is described as well as dresses. Sally should be featured, but she's still too young to be seriously romantic, except she thinks not.
chapter 2 London. Simon is told he'll become Sir Simon. various social connections as he sorts out his new role. Katherine takes up with Freddy's wife. There are a few social conflict/spats as they begin to learn to be spouses. Is there going to be a side trip to Denmark? The cloth deals need to be developed in any case. Need to introduce start of romantic tension. Is Katherine recruited/warranted here or later?
Simon approaches Freddy about getting money to Marie. Katherine hears about this and begins inquiries. Eventually Freddy's wife tells her a little. Simon has to come clean about it. They have more than a bit of an argument.
Chapter 3 Cambridge. Simon needs to learn ciphers, codes, secret inks and various aspects of tradecraft. Simon heads up alone because they aren't talking to each other. Normal nomenclater, maybe a playfair cipher, a couple of inks and how to use them, and the use of chalk and chips to monitor when you're watched. When and where does he get his iron cane? when and where does he get martial training, if any. Simon is pursued, while there by a local beauty, could even be a bit entangled. Remember just holding hands was considered risqué, so it could be completely innocent on his part.
Fennians strike on the trip? (Katherine, Aunt Emilia, Cousin?) Katherine's response is reported to her uncle and she is recruited. (but only after a reunion with Simon). Katherine is pursued by a young man, who doesn't understand the meaning of no.
Can connect with Katherine's cousins. (Is the unmarried one the interest? certainly could be for a diversion).
Chapter 5. Forgiveness.
Simon tells Katherine everything. The problem is now what do to with the two people who think they're in love with them. Decide to keep up the pretense of the argument and bring their pursuers together. Thus solving the problem. Katherine's still unmarried cousin is in on it and thinks it great fun.
Chapter 6. A college ball. A comedy of errors. Practicing their tradecraft Simon and Katherine dupe their amorata's into finding themselves in the same dark room. Misunderstandings and hilarity ensue. The two are 'compromised' even if they didn't do anything. (they do somethings, but nothing we'd consider problematic – as the man reaches to stroke her leg or simply kiss her hand she mumurs “oh Simon”, “what the hell?”) They really don't fit together. Katherine's cousin is a much better fit for the man. As they find out quickly. Trouble is everyone expects the two to get hitched soon.
Chapter 7. More confusion. Cousin really heartsick about man. He's beginning to take notice. Wishes he could be more forward, but can't because of his situation.
Chapter 8. An explosion. Katherine's married cousin's lab has an explosion. (they really didn't understand the dangers). The cousin's husband is fine – he's out of the way but a handsome young scholar is temporarily disabled. This makes him an object of romantic interest, especially for the woman who chased Simon.
Chapter 9. Conflict of Interest. The pair's wedding plans proceeds apace. Except things keep getting in the way. For example walking down the street they couple spy one or the other of their real loves and stare. Or at another ball, they dance with the wrong partners. The man goes out of town to deal with some estate business, and the woman is more or less literally thrown into the arms of her true love. Simon and Katherine have something to do with this. Possibly arranging a ride in the country or something that allows the accident to happen. (for example, since he's recovering, he could go in a carriage and she with him. It breaks down or has a horse go lame.).
Chapter 10. Regrets, and resolutions.
Chapter 11. Denmark ? Connection a Hessian captain Ewald is now General Ewald in the Danish army (REAL). Simon and Katherine arrive under cover of Freddy & wife. (Cover or Aegis of).
Packet boat 1-2 weeks of misery. Well could be but Katherine is game for anything.
So Simon has to know something about the banking/wool trade. Not a lot but enough to be believable. Guess what he learns in Chapter 10. Ewald should know Sir Reginald, which serves as the link. The man in Chapters 3,4,5 could be detailed to go with them. Awkward, but allows freedom of action for the other.
Chapter 12. Denmark ctd?
Chapter 13. Simultaneous back in Cambridge. Woman from 3,4,5 and the HYS begin to see more of each other. Woman sends a “Should we?” letter to man. Cousin distraught that he might be hurt.
Chapter 14. HYS and woman elope (or it seems like it – maybe post banns in his home parish).
Cousin sends letter to Man from 3,4,5. Goes home to father in London.
Chapter 15. Return from Denmark. Debriefing. (LONDON).
Chapter 16. Cousin and man 345 hook up. Might take a while to sort it out.
Final Chapter. I thought having Clarke being posted to the Mediterranean fleet would be a good idea. He can carry Simon and Katherine part way. Malta, Gibraltar or even Corsica (think the Brits still occupied it) Possibly southern Italy.