A tale of twins. The story starts with them rebelling against their parents. They go to the capital city and are caught up in the political events there.
The Earl Marrin and his men have been taken over by a firefly who has become human, and Darius, the male twin, gets drafted into the army. The special drug/spice (ashes of humans) sessera makes him keep losing his memory/agency and going along with what they want; meanwhile, all the waterwitches have been hunted down and some of them have hidden in another realm, linked to this world only by drops of water hidden in bottles.
The female twin, Laura, hides out with her cousin Randall and discovers she has waterwitch powers, though these are untutored and thus don't do much. She is set up to be with a boy of the streets who keeps her company along with his sister. Darius is friends with the firefly's son Perrian, but Franklin, a street boy is his real friend.
It was an okay read but for me a mediocre sort of fantasy, with very little depth to it. You never really got a chance to relate to the characters, and the emotional scenes seemed contrived. Three of the most interesting characters (Wincy, her fiance, Quinland, and her brother Randall) all die at the end and the ending seemed unsatisfactory in that we didn't really find out what was going to happen in the future, and the twins were never reunited with or even seemed interested in their parents.