She had a surreptitious relationship with her employee.
<a private investigator adept at taking surreptitious pictures of adulterous couples>
The letter didn't offer up the jewels, only shadowy suggestions about their disappearance, claiming that [heiress, Carolyn] Skelly, in a surreptitious trading of parcels with “a man in an ankle-length tweed overcoat,” had left a bag full of jewelry on the floor at J.F.K. —Mark Seal, Vanity Fair, December 2001
In the early evening as we gathered in the lobby beneath mounted elk heads and bear skins, the lights of the chandelier flickered mysteriously. But the teacher and I both spied the surreptitious action of the desk clerk, whose sheepish smile acknowledged that one brief hotel mystery had been solved. Other signs of pranking there included a “ghost” photo (displayed in a lobby album) that the clerk confided to me was staged, and some pennies, placed on the back of a men's room toilet, that from time to time would secretly become rearranged to form messages—like the word “why?” that I encountered. —Joe Nickell, Skeptical Inquirer, September/October 2000
The next week offered [FBI agent] Wiser the opportunity he had been waiting for. Ames was leaving the country, going to Ankara for a weeklong international conference on drugs. Wiser went to Bryant for permission to run a … surreptitious search of Ames' garbage. But the chief was dead set against it. —Tim Weiner et al., Rolling Stone, 29 June 1995