Troas is where Luke joins Paul's company. In Acts 16, after the Spirit forbade Paul to preach in Asia and did not permit entry into Bithynia, Paul and his party passed by Mysia and came down to Troas. There Paul saw a night vision of a man from Macedonia pleading, "Come over to Macedonia and help us." At that point the narrative shifts from "they" to "we," quietly showing that Luke, the Gentile physician, was now present. The Amplified Bible makes this explicit in verse 10, adding "including Luke." Luke and Paul immediately sought to go to Macedonia, concluding that God had called them to preach the gospel there, and they sailed from Troas by a straight course to Samothrace, then Neapolis and Philippi. Luke may have become a follower of Christ earlier, possibly on Paul's first journey, but Troas on the second journey marks the point where he became one of Paul's constant companions. Through that close association with someone of similar gifts of mind, Luke learned the difficult things of Paul's teaching and was prepared to write about Jesus Christ with clarity to Jew and Gentile alike. God used the trials they shared to perfect the irrevocable gifts He had given Luke.