What does the ending of the first season of the English drama Missing mean?

At the end of the play, Carl concealed the news that his apprentice's boyfriend was missing.

Missing is a Korean thriller, directed by Jin Chenghong and starring Seung Geun Moon, Choo Ja Hyun, Quan Shixian and Nan Shirley. The film mainly tells the story of Seung Geun Moon Interpol losing contact with his family and looking for his family. The film was released in Korea on March 9, 2009.

Missing describes a five-year-old boy who disappeared mysteriously while traveling to France with his parents in 2006. Eight years later, people confirmed that he was dead, but his father still had a glimmer of hope.