An 80-year-old Iranian-American was arrested Monday night when he returned to Tehran after visiting family and getting a medical exam in Dubai. Baquer Namazi was picked up at the Tehran airport and driven to his house for several hours of interrogation, then taken to the notorious Evin prison. His family, which posted about his arrest Wednesday on social media, has had no contact with him since.

Why should Iranian authorities arrest a retired civil servant with a heart problem, someone who, after many years with UNICEF, worked with Iranian nongovernmental organizations in his retirement and has spent his other time with family and friends?

The answer is not hard to discern. Last summer, Iran’s Intelligence Ministry prevented Mr. Namazi’s son, Siamak Namazi, an economist and business consultant, from leaving the country. He was regularly interrogated for months before being arrested in October. Four months have passed since his arrest, and no formal charges have been issued. Scattered remarks by authorities and members of Iran’s parliament suggest that the Intelligence Ministry wishes to implicate Siamak Namazi in a supposed U.S. plot to infiltrate and undermine the Islamic Republic by promoting business exchanges between Iran and the U.S. Iranian authorities have not produced a shred of evidence to support this fantastical idea. Nor has a coerced confession yet surfaced.

The arrest of Mr. Namazi–news of which quickly began circulating Wednesday on Twitter–seems a transparent attempt to pressure his son into such a false confession. His elderly father, who has a heart condition and other ailments, reportedly was contacted by an officer with Iran’s Revolutionary Guards and promised a visit with his son upon his return to Tehran. He was arrested before he had even emerged from the airport Monday.

Iran’s Intelligence Ministry, and its enablers in the judiciary, have been desperate to prove that the U.S. is scheming against the Islamic Republic through various means, including cultural and business penetration. A recent warning by Iran’s supreme leader, AyatollahAli Khamenei, about supposed U.S. tactics appears to have prompted intelligence officials to redouble their efforts. The end result is that innocent men and women are treated cruelly to satisfy security authorities’ whims; if a young man cannot be coerced into a false confession, then his father must be used as leverage.

This article was published originally here in The Wall Street Journal.

The opinions expressed here are those solely of the author.