Because this initiative was the first of its kind, the goal in Ede was to see whether such a project was even practical.

The untested nature of the project meant the organizers prepared as meticulously as possible.

The undercover patients developed their fictive biographies in months of meetings with an acting coach and a psychotherapist. “Ronald,” for example, was a middle-aged man with a history of aggression problems, and after a supposed suicide attempt he was taken to De Riethorst by an actor playing his brother. To make their stories believable, the patients memorized details about where their children went to school or which supermarket they shopped at, and the psychotherapist advised them on how to present their given mental illness convincingly.

To ensure their safety, the fake patients checked in via text message every three hours, and they carried letters identifying them as plants. A code word (“fireplace”) was in place if they had to communicate genuine distress to visitors. The visitors wore hidden cameras and microphones; the undercover patients did not.

The warning to the staff about the undercover patients made the project more amenable to Martien Opdam, a psychiatric nurse at De Riethorst who worked while the plants were there. Though he and his colleagues did wonder who the plants might be, he said: “You can’t keep doing that for two months. You go back to your routine.”

He said the experience was helpful. “It taught me not to go too much on autopilot,” he said.

Among the findings of the project were that patients frequently found it difficult to get information on their treatment and medications and that the sound of a staff member’s key chain jangling could be jarring to an already anxious patient.

Malingering one’s way into a psychiatric ward to report on conditions within has been a journalistic staple since as far back as 1887, when Nellie Bly got herself admitted to the insane asylum on Blackwells Island (now Roosevelt Island) in New York City. Similar endeavors have been the subject of many books and television documentaries over the years.

The best-known scientific example remains the experiments by David Rosenhan, a psychologist. He and seven other “pseudopatients” got themselves admitted to a dozen hospitals by pretending to hear voices, and the study, published in Science magazine in 1973 as “On Being Sane in Insane Places,” is still widely seen as a critique of psychiatric diagnosis.