This is book 5 of the "Family D'Alembert" series.

This note contains spoilers for the book.

An attempted coup at the wedding of the imperial heir.

The nobility are experiencing a high accident rate -- and the most suspicious accidents all happen to people with heirs either incompetent, or not very supportive of the imperium. Then a chartered ship of nobles is hijacked, and the pirates know the passenger list, and are prepared to space out-of-hand people not on it.

Then Lady A and those robots show up again.

All foiled at the last second by various members of the Family D'Alembert.

We also get to visit Pias' home planet. He gets read out of his family -- convenient in one way, since they wouldn't understand why he wanted to serve the SOTE, or marry an outsider woman. (Gypsy heritage).