Sixth of the Family D'Alembert series; which is mostly by Stephen Goldin, though Smith published one story in that setting.

He's taken to splitting the two teams of agents, and thus getting two plots per book regularly. One of the plots involves religious subversion on Purity, a world of religious conservatives. They forgot to give themselves a hierarchical authority, though, so Pias sets up as an "exhorter" and argues it's heresy to turn your back on god's gifts. And eventually manages to corner another of those damned robots. Apparently it wasn't politically feasible to just enforce the law against private armies.

Meanwhile, the other team has found a weapons factory on a Mercury-like planet, and get stranded far from base (having killed the people planning to assassinate them). They, too, get back, and bring home the knowledge of the planet's location, which implicates the duke of the known inhabited planet in that system.