The fourth and final book in the Warden Rhombus tetralogy, the main Command of the Armed Forces - the very heart of the Confederation has been penetrated by an alien robot spy. Security Service analysts have no doubt that aliens are recruiting agents on the four planets of the Varden Rhombus. The investigation is entrusted to the best agent of the Confederacy. and on Lilith, neither on Cerberus, nor on Charon, no traces of aliens could be found. The last planet left is Medusa.