Johan Floderus, an EU diplomat, has spent two years in an Iranian prison.

Authoritarian governments have learned they can trade Western humanitarian workers and journalists for convicted killers and intelligence agents.

The first time anybody realized Johan Floderus had been arrested was when he didn’t get off the plane.

The 33-year-old Swedish diplomat had arrived at Tehran’s Imam Khomeini International Airport to fly home after a week visiting friends in Iran. It took several days for his friends and family to work out he was in the feared Evin Prison — and more than a year before his arrest was made public.

Two years after his detention on April 17, 2022, Floderus — an employee of the EU’s diplomatic service — is still behind bars. Though he’s been accused of espionage, those familiar with his case say he’s more likely the latest example of Iran’s campaign of hostage diplomacy, in which Tehran arrests Westerners to exchange them for officials held in Europe for spying, terrorism or human rights violations.