In the train tunnel through Copenhagen, the spy relaxed and turned on the overhead light to read a romance novel. For exactly three minutes, timed by her excellent agency-issued watch, she allowed herself an illusion of a husband, a home and mildly pornographic sex. Then the alarm went off(more) and she killed the person next to her with a small pen knife as planned.
She got off at the next stop.
The next time she had sex, it was with another spy in the elevator at her agency between floors. They set off the alarm to buy a few more minutes of time so they could both reach orgasm with a little more leisure.
For her entire career, she was haunted by a phrase, "I am a spy who came in from the cold." Before she retired, she was sent to do one last kill which she did with exhausted efficiency. She moved to Bermuda, threw away her watches and her weapons and moved through the sunlight, a pleasant elderly woman in a broad straw hat with a sometimes startled broad smile as if startled by her happiness.