4 ideas
C'mell, a cat-derived underperson who works as a girlygirl entertaining off-world visitors at Earthport, lets the hidden bird-derived underperson leader E'telekeli channel through her into the mind of the Lord Jestocost. While the Lords of the Instrumentality are gathered in an emergency session at the Bell, E'telekeli uses Jestocost's access to copy records the underpeople need to press their claims.
Underpeople are made from animals and shaped into human form for labor and service. Because the law classes them as property rather than persons, they can be killed or discarded at will, whatever their intelligence or feeling. Their oppression rests on a legal definition, not on any real difference in capacity.
Change in a rigid system happens when a sympathetic insider lends access to the organized oppressed, while each side keeps the other's role invisible. The underpeople cannot reach the levers without him. Secrecy is what lets the alliance work at all.
C'mell's commitment to the cause is bound up with a love for Jestocost that the social order forbids, and he barely recognises it until late. Seen this way, a political alliance can be driven by private devotion that is never openly spoken. Much of the cost of reform falls on the person whose feelings the system gives no way to express.