The Synectic Snare (Book 2 of the Celestriad‪)‬

Celestra's once-peaceful allies, the Narvellans, have suddenly staged a coup, turning their hosts' planet into an industrialised police state and enslaving the population. It's rumoured that the Narvellan homeworlds are being controlled by a sinister group mind, but is this true? If so, how can it be found and shut down?
Laura's inexperienced band of conspirators will endure danger, tragedy and personal sacrifice in their quest to liberate two civilisations.