Ranson took the key from the massive plastic door as he backed through the entrance. Once in the hall, he slammed the door shut, locked Maxwell and his men in the room. Then, dropping the gun into his pocket, he ran swiftly down the corridor to the main entrance of headquarters. In the hall a patrolman glanced at him suspiciously, halted him, but a wave of Ranson's T.I. card put the man aside.
Free of headquarters, Ranson began to run. Only a few moments, he knew, before Maxwell and his men blasted a way to freedom, set out in pursuit. Like a lean gray shadow Ranson ran, twisting, dodging, among the narrow streets, heading toward Haller's house. Mercis was a dream city in the wan light of the moons. One in either side of the heavens, they threw weird double shadows across the rippling canals, the aimless streets. Sleek canal-cabs roared along the dark waterways, throwing up clouds of spray, and on the embankments, green-eyed, bulge-headed little reddies padded, silent, inscrutable, themselves a part of the eternal mystery of Mars.
Haller's house stood dark and brooding beside the canal. Captain Maxwell's men had completed their examination and the place was deserted. Ranson stepped into the shadow of the clump of fragrant fayeh bushes, where the unknown musician had stood; there was little danger, he felt, of patrolmen hunting for him at Haller's house. The captain had little faith in copybook maxims about the murderer returning to the scene of the crime.
Ranson stood motionless for a moment as a canal boat swept by, then drew from his pocket a heavy black tube. He tugged, and it extended telescopically to a cane some four feet long. The cane was hollow, a tube, and the head of it was large as a man's two fists and covered with small dials, gauges. This was the T.I.'s most cherished secret, the famous "electric bloodhound," by which criminals could be tracked.
Ranson touched a lever and a tiny electric motor in the head of the cane hummed, drawing air up along the tube. He tapped the bank where the unknown musician had stood, eyes on the gauges. Molecules of matter, left by the mysterious serenader, were sucked up the tube, registered on a sensitive plate, just as delicate color shades register on the plate of a color camera.
Ranson tapped the cane carefully upon the ground, avoiding those places where he had stood. Few people crossed this overgrown embankment, and it was a safe bet that no one other than the strange musician had been there recently. The scent was a clear one, and the dials on the head of the cane read R-2340-B, the numerical classification of the tiny bits of matter left behind by the unknown. The theory behind it was quite simple. The T.I. scientists had reasoned that the sense of smell is merely the effect of suspended molecules in the air acting upon sensitive nerve filaments, and they knew that any normal human can follow a trail of some strong odor such as perfumes, or gasoline, while animals, possessing more sensitive perceptions, can follow less distinct trails. To duplicate this mechanically had proven more difficult than an electric eye or artificial hearing device, but in the end they had triumphed. Their efforts had resulted in the machine Ranson now carried.
The trial was, at the start, clear. Ranson tapped the long tube on the ground like a blind man, eyes on the dial. Along the embankment, into a side street, he made his way. There were few abroad in this old quarter of the city; from the spaceport came the roar of freighters, the rumble of machinery, but here in the narrow winding streets there was only the faint murmur of voices behind latticed windows, the rustle of the wind, the rattle of sand from the red desert beyond the city.
As Ranson plunged further into the old Martian quarter, the trail grew more and more confused, crossed by scores of other trails left by passersby. He was forced to stop, cast about like a bloodhound, tapping every square foot of the street before the R-2340-B on the dial showed that he had once more picked up the faint elusive scent.
Deeper and deeper Ranson plunged into the dark slums of Mercis. Smoky gambling dens, dives full of drunken spacehands and slim red-skinned girls, maudlin singing ... even the yellow glare of the forbidden san-rays, as they filtered through drawn windows. Unsteady figures made their way along the streets. Mighty-thewed Jovian blasters, languid Venusians, boisterous earthmen ... and the little Martians padding softly along, wrapped in their loose dust-robes.