This is an intriguing case of the Hotel Rössli in Unterbach, a serene village in the Swiss Alps. This century-old lodge, known for its picturesque views and rustic charm, became the unlikely center of an international espionage controversy involving the United States, China, and Switzerland.

The hotel's proximity to a Swiss military airstrip, which will house advanced F-35 fighter jets, piqued the interest of U.S. intelligence. The airstrip, only partially fenced and frequently crossed b...