Trent judged this to be a promising state of things. He lifted off from Dorade. On the next leg of his journey he instructed his crewmen in the use of the just-acquired weapons. In particular he drilled them in the fine art of combat inside a spaceship's elquences of compartments, tanks, holds, and other places they'd never imagined as combat areas. They found the instructions fascinating. He informed them of practical but unusual methods by which men in spaceboats could board other space craft, using shaped charges against a metal hull to give them entry. These instructions, of course, were to prepare against pirates.
The Yarrow's crewmen were charmed. They formed a zestful conviction that Captain Trent planned some highly profitable piracy himself. They learned their novel lessons with enthusiasm and hope.
The Yarrow went on its way. Trent's several-times-great grandfather would have kept his crew chipping paint or tightening or slacking off stays to adjust to differences of humidity from day to day. If they were merchant seamen, they already knew how to fight. But Trent exercised his crew with weapons.
They anticipated interesting consequences of their new combat efficiency. They looked at Trent with bright eyes, waiting for him to tell them they were about to capture a space liner loaded with treasure and with terrified and hence docile females.
He gave them no such information, but he did keep them busy. Presently the Yarrow landed on Midway. He went aground, alone. He asked questions. He admitted that he planned to go trading in the Pleiads.
Officials on Midway warned him solicitously. Only one ship had left Midway for the Pleiads in months. None at all had come from them. The one ship to risk going in was the Hecla, and she'd lifted off only the day before. Her skipper'd judged from the latest reports of missing ships that the pirates were working on the far side of the Pleiad group. He was making a full-power dash for Loren. Trent had better not imitate him.
But Trent did. He lifted the Yarrow off Midway after only three hours aground. Immediately she was in space again he had the small-arms weapons passed out once more.
For four days out of Midway the Yarrow drove steadily, in overdrive and of course in illimitable isolation. She was surrounded by her overdrive field. Through it no light could pass, nor any message of any kind but one. Every instrument aboard her, made to report on the universe outside, now read zero. It was as if there were no cosmos, no galaxy, no existence beyond the ship's hull plates. The viewports viewed nothing. The communicators received nothing. The Yarrow was isolated as earlier generations could not have imagined. In overdrive a ship is practically in another and an empty universe, in which nothing ever happens.
But on the fourth shipday out from Midway one solitary instrument gave a reading. One dial-needle stirred, in the control room. One detector-needle moved the minutest possible trivial indication. A light glowed. The spaceman on control room watch notified Trent through the loudspeaker in the captain's cabin.
"Captain, sir, the drive-detector's registering."
"I'll be there immediately," said Trent.
He was. It was less than five yards from his cabin to the control room, but he hurried. The broad instrument board faced him as he entered, with all its dials and indicators above the equally broad but less cluttered lower control panel. Underneath every instrument either a green or an amber light told that each unit of the ship's equipment either operated normally, or was ready to do so when the ship broke out of overdrive. But the light under the overdrive detector shone red.
"No change as yet, sir," said the man on watch.
Trent grunted. He sat down in the pilot's chair. Almost immediately he reversed the Yarrow's drive. It began to cut down her speed from unthinkable overdrive-velocity to thousands of miles a minute, then to hundreds, to tens.
The detector reported stronger and stronger indications of another over-drive operating within another ship a—now—relatively trivial number of miles away. It would have to be in a ship, of course. And that ship would be informed by a detector in its control room of the Yarrow's existence and near presence.
Trent threw a switch. A panel of signal-analyzing instruments lit up. He set to work with them.
There was silence save for that small assortment of noises any ship makes while it is driving. It means that the ship is going somewhere, and hence that it will eventually arrive somewhere. A ship in port with all operating devices cut off seems gruesomely dead. Few spacemen will stay aboard ship in a spaceport. The silence is too oppressive.
The signal-analyzer clicked. It had determined the bearing of the other overdrive field. Lighted numerals preserved the information while the analyzers investigated other items. The detected field was very faint. Its bearing was ten-forty to the Yarrow's course. Its own course—
It had no course. If one allowed for the Yarrow's motion, the other ship must be standing still. But this was light-years away from Midway, and Midway was still the nearest world. It was not normal for a ship to lie still in space between the stars. Trent did something more abnormal still. He headed the Yarrow toward the overdrive signal source.
He pushed the all-hands-alert button. Speakers all over the ship emitted the raucous warning of probable emergency. He spoke into a microphone, and the same speakers echoed his words with a peculiar choral effect.
"Load small arms," he ordered curtly. "Take combat posts. Rocket launchers to the airlocks. No launching without orders."
He settled more firmly in the pilot's chair, and the man on watch drew back and began to get out the spacesuits the control-room occupants might need next. Trent continued to watch the dials of the signal-analysis devices. He had only instrument readings to go by now, but in all other respects this development in the journey of the Yarrow was like the sighting of a sail when one of his ancestors captained a trading vessel in the eighteenth century. The report of a reading on the drive detector was equivalent to a bellowed "Sail ho!" from a sailing brig's crosstrees. Trent's painstaking use of signal-analysis instruments was equal to his ancestor's going aloft to use his telescope on a minute speck at the horizon. What might follow could continue to duplicate in utterly changed conditions what had happened in simpler times, in sailing ship days.
The Yarrow's mate came in.
"Spacesuits, sir?" he asked stolidly.
"Better put them on, yes," agreed Trent. He didn't take his eyes from the instruments. The mate gave the order. He put on a spacesuit himself, from the back wall of the control room.
"Any other orders, sir?"
"Eh? Yes. Make sure the engineer's gadget is set for operation. We might as well try it out. But the engineer's the kind of putterer who'll constantly be trying to improve it. If he's done anything, make him stop and get it ready for use."
"Yes, sir," said the mate.
"You'd better know what's going on," added Trent. "There's an overdrive field out there ahead. It's of detection strength only; it isn't strong enough to affect the ship that's emitting it. But it should mean that our drive has been picked up too. Yet we're headed for it and it hasn't moved. You figure that out!"