The _Sirius_ was brought up beside the heptagon, so that her main air-lock was against one of the yawning holes in the green metal wall of the enemy. There she was anchored by tractor beams, and the two hundred picked men of the I-P police, in full space equipment, prepared to board the gigantic fortress of the void. Brandon sat tense at his controls, ready to send his beam ahead of the troopers against any hexans that might survive in some as yet unpunctured compartment. General Crowninshield sat beside the physicist at an auxiliary board, phones at ears and four infra-red visiray plates ranged in front of him; ready through light or darkness to direct and oversee the attack, no matter where it might lead or how widely separated the platoons might become before the citadel was taken. The space-line men--the engineers of weightless combat--led the van, protected by the projectors of their fellows. Theirs the task to set up ways of rope, along which the others could advance. Power drills bit savagely into metal, making holes to receive the expanding eyebolts; grappling hooks seized fast every protuberance and corner; points of little stress were supported by powerful suction cups; and at intervals were strung beam-fed lanterns, illuminating brilliantly the line of march. Through compartments and down corridors they went, bridging the many gaps in the metal through which Brandon's beams had blasted their way; guided by Crowninshield along the shortest feasible path toward the little projector room in which Kromodeor, the wounded Vorkul, lay. There were so many chambers and compartments in the heptagon that it had, of course, been impossible to puncture them all, and in some of the tight rooms were groups of hexans, anxious to do battle. But the general's eye led his men, and if such a room lay before them, Brandon's frightful beam entered it first--and where that beam entered, life departed.