I'm never quite certain whether Brust, at the time he was writing Teckla, was going through struggles in his own relationship with his significant other, or not, but he certainly captures the emotions well in Teckla. Vlad finds out that Cawti has been concealing something from him; that she's been spending time in the Eastern quarter of Adrilankha, working with a group of revolutionaries trying to raise the consciousness of the masses, more or less. The tribe of Teckla has always been the lowest of the low, and their labor is mostly responsible for feeding the Empire, but they are treated with contempt, poorly educated, unwashed...you get the picture.
Vlad is, of course, understandably upset that she has been doing this for months without telling him about it, and equally upset that she's gotten involved with a cause which he understands not in the slightest. It seems that Cawti has caught the reformation bug, and decided that her former profession of assassin was immoral, so she is trying to do good works instead. The implied criticism of Vlad's line of work does not go unnoticed, but their marital troubles aren't something that can readily be solved by the application of a dagger in the right location, so Vlad flails about for most of the novel, trying to figure out how to protect Cawti from the retribution that will most certainly follow, from either the Jhereg, whose businesses are being disrupted by the rabble rousers, or the Empress, whose city could grind to a halt if the Teckla do not bring their goods to market.
A difficult read, emotionally, for anyone who has experienced a love gone awry, and perhaps a key turning point in the series for Vlad.