haben."

"Good guessing," approved the masked man cheerfully. He motioned Manning and Dugan toward where a small skiff lay beached between the piles. "Help me launch this. First, though, turn your units up to full power—like this—so they'll cover the boat."

Manning was startled at the man's bravado; as all three laid hold of the boat, he whispered anxiously, "Won't they hear—"

"Not if we shouted our heads off," the other answered. "With these units going, we're not only invisible, but inaudible and practically intangible. I've walked through a cordon that was closing in on me with linked arms." He sprang nimbly into the bow of the boat. "Grab an oar, you two, and make yourselves useful. I've been through a lot of trouble on your account." He seemed to decide that introductions were finally in order. "My name's Jerry Kane. At any rate, it's my favorite alias."

Manning and Dugan named themselves and fell to rowing. "Downstream," said Kane, and he gazed back at the bridge with interest as they pulled away. Manning glanced back over his shoulder; there were dark figures swarming on the bridge, and lights, and a car had stopped there; even as he looked a searchlight beam swayed out across the water, moving systematically back and forth. For a moment it fell full upon the rowboat, and Manning ducked involuntarily; but the light passed on and there was no outcry, no shots came.

Manning said hoarsely, "That light was on us! It didn't go through us, or anything of the sort. A body that reflects light is visible. So how the devil—"

"We're not optically invisible," answered Kane amusedly. "So far as I know, that's a physical impossibility. Actually, those Germans saw us, but they didn't notice us. Ever catch yourself looking right at something and not seeing it, because it was too familiar or because you were thinking about something else? That's the effect the field has. Anything in the middle of it hides behind a psychic block in the mind of whoever looks at it. That's why it works on hearing, too, and even on touch. It's not perfect; if you set off a magnesium flare in front of somebody, or punched him in the nose, he'd notice something was up—but hardly before. When you get acquainted with the effect it makes you feel like a ghost. Back in that cafe, I had to shout in your ear till I deafened myself before I could make you hear."

They glided down the current, and the lights and voices around the bridge receded rapidly. As 

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