Markus Imboden’s “Der Verdingbub” (The Foster Boy), a moving drama about a dark and nearly forgotten period in the country’s recent history, has become the most successful Swiss film in the past five years, so far garnering $3.6 million at the local box office and drawing some 230,000 moviegoers.

The 1950s-set film follows a boy who is taken from his parents and sent to work on a farm as a “Verdingbub,” or contract child — a practice that lasted from the early 1800s until the 1960s.

The government policy deprived families of custody if they were poor or didn’t live according to middle-class social mores; that often included single or divorced parents. Many contract children experienced emotional, physical and sexual abuse at the hands of foster parents, who used such children as farm hands.

“Those who suffered felt stigmatized and never spoke about it to their families,” says C-Films producer Peter Reichenbach.

The pic’s star, Max Hubacher, who was feted as Switzerland’s Shooting Star at the recent Berlinale, says that before he was cast, he knew nothing about this dark chapter in Swiss history.

“It’s good, because the topic is now being talked about in public,” Hubacher says. “It was a taboo topic in Switzerland. But people are learning about it now, especially young people.”

The subject also is being showcased in the current exhibition “Verdingkinder Reden” (or Contract Children Speak) in Zurich, which offers first-hand testimony from former contract children.