The Ghosts, book 7. Spoilers ahead for the earlier books.
For instance, the negotiations over the end of the war. Caina and Corvalis run the capital's coffee shop to garner gossip for the Ghosts, but their task for this book is to protect the emissary. Meanwhile, they happened on foreign assassins trying to capture a pregnant foreign woman and kill her father, a former gladiator. This strikes them as, at least, a remarkable coincidence.
The tale involves smoke bombs, coffee, the phoenix and its ashes, an archer on a rooftop, the secret of becoming a Master Alchemist, and more.