orbit of Mars,
coming diagonally and heading very nearly for the Sun. But it's not a
comet."

The thing was indeed inexplicable; for many weeks now, astronomers had
been studying it. This was early summer of the year 2070 A.D. All of
us had recently returned from those extraordinary events I have
already recounted, when we came close to losing Johnny Grantline's
radiactum treasure on the Moon, and our lives as well. My ship, the
_Planetara_, in the astronomical seasons when the Earth, Mars, and
Venus were within comfortable traveling distances of each other, had
carried mail and passengers from Greater New York to Ferrok-Shahn, of
the Martian Union, and to Grebhar, of the Venus Free State. Now it was
wrecked on the Moon.[1]

[Footnote 1: See "Brigands of the Moon", Ace Book, D-324]

I had been under navigating officer of the _Planetara_. Upon her, I
had met Anita Prince, whose only living relative, her brother, was
among those killed in the struggle with the brigands; Anita and I were
soon to marry, we hoped.

I was waiting now in Greater New York upon the decision of the Line
officials regarding another spaceship. Perhaps I would have command of
it, since Captain Carter of the _Planetara_ had been killed.

It was a month or so before that adventure, April, 2070, that this
mysterious visitor from interstellar space first appeared upon our
astronomical horizon. A little thing, at first, a mere unusual dot, a
pinpoint on a photo-electric star diagram which should not have been
there. It occasioned no comment at the time, save that some thought it
might be another planet beyond Pluto; but this was not taken seriously
enough to get into the newscasts. None of us had heard about it as
late as May, when the _Planetara_ set out on what was to be her final
voyage.

Presently, it was seen that the object could not be a planet of our
solar system; Coming in at tremendous speed, it daily changed its
aspect, gathering velocity until soon it was not a dot, but a streak
on every diagram-plate.

In a week or so the thing passed from an astronomical curiosity to an
item of public news. And now, early in June, when it had cut through
the orbit of Jupiter and was approaching that of Mars, fear was
growing. The visitor was a menace. No astronomical body could come
among us, with a mass as great as a fifth of the Moon, without causing
trouble.

The newscasters, with a ready skill for lurid possibilities, were
blaring of all so