For a long time we stared silently at the fluttering line dancing across the oscilloscope screen, bathing our tiny dome in its weird greenish light. It was eerily fascinating, hypnotic. The line never stood still; it jabbered and stuttered, a series of millions of little peaks and nulls, changing almost too fast for the eye to follow, up and down, calling to us, speaking to us, up, down, never still, never quiet, constantly flickering its unknown message to us. [Illustration: _The line never stood still; millions of little peaks and nulls calling to us, speaking to us, never still, never quiet, constantly flickering its unknown message to us._] "Can it be ... people?" Rizzo wondered. His face, bathed in the greenish light, was suddenly furrowed, withered, ancient: a mixture of disbelief and fear. "What else could it be?" I heard my own voice answer. "There's no other explanation possible." We sat mutely for God knows how long. Finally Rizzo asked, "What do we do now?" * * * * * The question broke our entranced mood. What do we do? What action do we take? We're thinking men, and we've been contacted by other creatures that can think, reason, send a signal across seven hundred lightyears of space. So don't just sit there in stupified awe. Use your brain, prove that you're worthy of the tag _sapiens_. "We decode the message," I announced. Then, as an after-thought, "But don't ask me how." We should have called McMurdo, or Washington. Or perhaps we should have attempted to get a message through to the United Nations. But we never even thought of it. This was our problem. Perhaps it was the sheer isolation of our dome that kept us from thinking about the rest of the world. Perhaps it was sheer luck. "If they're using lasers," Rizzo reasoned, "they must have a technology something like ours." "Must _have had_," I corrected. "That message is seven hundred years old, remember. They were playing with lasers when King John was signing the Magna Charta and Genghis Khan owned most of Asia. Lord knows what they have now." Rizzo blanched and reached for another cigaret. I turned back to the oscilloscope. The signal was still flashing across its face. "They're sending out a signal," I mused, "probably at random. Just beaming it out into space, hoping that someone, somewhere will pick it up. It must be in some form of code ... but a code that they feel can be easily cracked by anyone with enough intelligence to realize that there's a message there." "Sort of an interstellar Morse code." I shook my head. "Morse code depends on both sides knowing the code. There's no key." "Cryptographers crack codes." "Sure. If they know what language is being used. We don't know the language, we don't know the alphabet, the thought processes ... nothing." "But it's a code that can be cracked easily," Rizzo muttered.