Ghost in the Cowl by Jonathan Moeller

book 1 of Ghost Exile, but very much after Ghosts, so spoilers for the earlier series ahead.

Starting with how Caina, on her way to her exile as a circlemaster in foreign Istarinmul, is brooding and grief-stricken and throws knives at the mast -- well enough to get a job offer from a circus.

Once there, she goes to piece together what happened to the Ghosts who vanished there, and meets the sister of the old circlemaster, running her coffee shop, and hears about the slavers' drive to get ever more slaves.  When a forged document is used to seize the sister's sons and servants, Caina devises a mad plan to rescue them.

The rest involves losing at cards, claiming to have lice, forging a key, a rampage against slavers, the drug wraithblood that is plaguing the city, a woman who can calculate Caina's height and weight, and more