Twisting and turning beside the slumbering Tereza, he recalled something she had told him a long time before in the course of an insignificant conversation.

From the very beginning of the occupation, Russian military airplanes had flown over Prague all night long. Tomas, no longer accustomed to the noise, was unable to fall asleep.

Even then, her words had left Tomas in a strange state of melancholy, and now he realized it was only a matter of chance that Tereza loved him and not his friend Z. Apart from her consummated love for Tomas, there were, in the realm of possibility, an infinite number of unconsummated loves for other men.

We all reject out of hand the idea that the love of our life may be something light or weightless; we presume our love is what must be, that without it our life would no longer be the same; we feel that Beethoven himself, gloomy and aweinspiring, is playing the Es muss sein! to our own great love.

They had been talking about his friend Z. when she announced, If I hadn't met you, I'd certainly have fallen in love with him.

Tomas often thought of Tereza's remark about his friend Z. and came to the conclusion that the love story of his life exemplified not Es muss sein! (It must be so), but rather Es konnte auch anders sein (It could just as well be otherwise).

He had gone back to Prague because of her. So fateful a decision resting on so fortuitous a love, a love that would not even have existed had it not been for the chief surgeon's sciatica seven years earlier. And that woman, that personification of absolute fortuity, now again lay asleep beside him, breathing deeply.

Seven years earlier, a complex neurological case happened to have been discovered at the hospital in Tereza's town. They called in the chief surgeon of Tomas's hospital in Prague for consultation, but the chief surgeon of Tomas's hospital happened to be suffering from sciatica, and because he could not move he sent Tomas to the provincial hospital in his place. The town had several hotels, but Tomas happened to be given a room in the one where Tereza was employed. He happened to have had enough free time before his train left to stop at the hotel restaurant. Tereza happened to be on duty, and happened to be serving Tomas's table. It had taken six chance happenings to push Tomas towards Tereza, as if he had little inclination to go to her on his own.

It was late at night. His stomach started acting up as it tended to do in times of psychic stress.

Once or twice her breathing turned into mild snores. Tomas felt no compassion.

All he felt was the pressure in his stomach and the despair of having returned.