"Tricia McMillian?" he said. "What are you doing here?"
"Same as you," she said, "I hitched a lift. After all with a degree in Maths and another in astrophysics what else was there to do? It was either that or the dole queue again on Monday."
"Infinity minus one," chattered the computer, "Improbability sum now complete."
Zaphod looked about him, at Ford, at Arthur, and then at Trillian.
"Trillian," he said, "is this sort of thing going to happen every time we use the Improbability drive?"
"Very probably, I'm afraid," she said.

The Heart of Gold fled on silently through the night of space, now on conventional photon drive. Its crew of four were ill at ease knowing that they had been brought together not of their own volition or by simple coincidence, but by some curious principle of physics — as if relationships between people were susceptible to the same laws that governed the relationships between atoms and molecules.
As the ship's artificial night closed in they were each grateful to retire to separate cabins and try to rationalize their thoughts.