Over uncounted millennia, Glieseians, a telepathic species, with mollusk-like bodies and frail arms that move on lubricated, muscular feet, like snails but have brains that equal nearly sixty percent of their body weight, have assumed the roles of observers, investigators, and interventionists, helping determine the developmental pathways taken by inhabitants of other planets in the Milky Way.

As Observers, Mxpan and Zerpall are expected to perform only that role—contact with natives of planets to which they are assigned is unacceptable. However, since M and Z are the Frick and Frack of the Glieseian Ministry of Observation, Investigation, and Intervention (MOII), the pair is imprisoned twice, banished from two solar systems, threatened with selective destruction by targeting their DNA, trapped in android bodies after a faulty brain essence transfer, and forced into an ethically convoluted situation after uncovering a secret about their distant predecessors.