Most of the screen seemed normal. The three curved segments, representing joined fields of space extending around the sides and aft of the _Avenger_, showed the normal inky, star-studded black. But it was different with the forward screen. In the center, where the growing image of their green home planet should have been, was only blackness--unrelieved emptiness. "From the looks of that, Mister McTavish," the Captain said sternly, "you have a few stalemated wires." * * * * * The Engineer's thin face flushed. His long nose twitched, and his grey eyes smouldered with professional indignation. "Begging your pardon, Sir," he objected. "If any coordinates had failed, the entire screen would blank out--and stay blanked, until I was notified. I would authorize partial operation only while the condition was being adjusted, Sir." "Do you mean," asked Lieutenant-Commander Clemens, his voice dropping ominously, and one arm gesturing heavily at the empty blotch, "that--that--" "That whatever you see is there," finished McTavish. "Or isn't there," he amended drily. Captain McPartland saw Ray Control Officer Roberts get up quietly from before the chess board, and walk over to his station. Roberts, his round face impassive, brown eyes thoughtful, slid into the chair before his microphone, and ran long, slim fingers lovingly over his calculators. The Engineer, too, at a nod from Jon moved over to his station. His grey eyes were soft with pride as they looked over the exact scale replica of the _Avenger_ on the table before him. Within the transparent hull, vari-colored filaments glowed with the pulse of the ship, tracing out the perfect functioning of every mechanism. McPartland looked at the other, then back at the view screen, and his full lips tightened. He could feel the tenseness of the three officers as he spoke into the intra-ship. "Get me Terra Patrol Base on the ship visa-phone," he ordered Radio Officer Holdern. "Sorry, Sir," was the crisp response, "I've been trying to raise Terra since the machinist's mate found your instrument in perfect order. Terra doesn't answer!" Jon's blue eyes hardened. "Get Mars Patrol Base!" he said softly. As he moved to the visa-phone, Clemens took over the intra-ship, plugging in his headset. His gloomy expression deepened when the instrument buzzed immediately. "Navigation reports integrators acting improperly, Sir," he relayed. "Radar shows negative from direction of Terra." "Impossible!" the Captain gasped, face suddenly wooden. "Lieutenant Parek's exact comment, Sir," Clemens said sadly. He ran a nervous hand through thinning blond hair beneath his headset. His pale eyes were expectant. "Tell Navigation to hold course," McPartland said calmly. Something in his voice super-charged the already taut atmosphere of the Control Room, bringing an eager smile to the face of Engineer McTavish.