The document discusses Mark, who initially quit a missionary journey with Paul and Barnabas but later rejoined them, as shown through several Bible passages. It notes that Mark started well but quit halfway through the mission to Acts 13:13. However, later passages like Colossians 4:10 and Philemon 1:24 indicate that Mark had come back, with 2 Timothy 4:11 suggesting that Mark was now profitable to Paul for ministry work.