The laws of action and reaction work equally well, whether or not the action is intentional. The jets of gas served as natural rocket thrusters, accelerating the comet in unexpected directions, throwing it off its carefully calculated course.

But other jets flared almost at once, artificial ones that compensated for the uncontrolled thrust. The control thrusters had to fire more and more frequently as the comet moved in closer to the inner planets of the star system.

It soon became plain that the comet was heading straight for a planet in the inner system, a world of blue and brown and tan, a world that was nearly all water in the southern hemisphere, and nearly all dried-out desert in the north.

The comet fell in toward the planet, closer and closer. The comet warmed as it came in nearer to the star the planet orbited. Its surface began to boil and vaporize, gases and dust blowing off into space, forming up into a tail that stretched itself out behind the comet.

The comet suddenly broke up. The fragments spaced themselves out into a neat line, like beads on a string.

The fragments moved closer, closer to the planet.

“Move from time factor positive one hundred to positive factor ten time dilation,” said a disembodied voice in the darkness.

Time seemed to slow, the fragments suddenly moving at a fraction of their original velocity, easing themselves slowly down out of orbit.

“Give me a view closer to Inferno,” the same voice commanded, and the image suddenly swelled in size.

“That’s still way too fast. Time dilation to negative factor five,” the voice ordered.

Once again, the clock slowed down, but even so, events moved quickly. The comet fragments were moving with incredible speed as they slammed into the planet’s upper atmosphere, and even with time slowed to a fifth its normal speed, it still took scant seconds for the fragments to force their way down through the atmosphere and slam into the planet.