"Er, Designer People."
"What?"
"The Sirius Cybernetics Corporation were awarded a huge research grant to design and produce synthetic personalities to order. The results were uniformly disastrous. All the "people" and "personalities" turned out to be amalgams of characteristics which simply could not co-exist in naturally occurring life forms. Most of them were just poor pathetic misfits, but some were deeply, deeply dangerous. Dangerous because they didn't ring alarm bells in other people. They could walk through situations the way that ghosts walk through walls, because no one spotted the danger.
"The most dangerous of all were three identical ones - they were put in this hold, to be blasted, with this ship, right out of this universe. They are not evil, in fact they are rather simple and charming. But they are the most dangerous creatures that ever lived because there is nothing they will not do if allowed, and nothing they will not be allowed to do..."
Zaphod looked at the dim yellow lights, the two dim yellow lights. As his eyes became accustomed to the light he saw that the two lights framed a third space where something was broken. Wet sticky patches gleamed dully on the floor. Zaphod and the official walked cautiously towards the lights. At that moment, four words came crashing into the helmet headsets from the other official.
"The capsule has gone," he said tersely.
"Trace it" snapped Zaphod's companion. "Find exactly where it has gone. We must know where it has gone!"
Zaphod slid aside a large ground glass door. Beyond it lay a tank full of thick yellow liquid, and floating in it was a man, a kindly looking man with lots of pleasant laugh lines round his face. He seemed to be floating quite contentedly and smiling to himself.
Another terse message suddenly came through his helmet headset. The planet towards which the escape capsule had headed had already been identified. It was in Galactic Sector ZZ9 Plural Z Alpha.
The kindly looking man in the tank seemed to be babbling gently to himself, just as the co-pilot had been in his tank. Little yellow bubbles beaded on the man's lips. Zaphod found a small speaker by the tank and turned it on. He heard the man babbling gently about a shining city on a hill.
He also heard the Official from the Safety and Civil Reassurance Administration issue instructions that the planet in ZZ9 Plural Z Alpha must be made "perfectly safe."