History and tradition are filled with twists and turns, highs and lows, glories and embarrassments. Sometimes, though, sorting through it all is the path to truth.
When the apostles were sent into the world to convert it, many went beyond the boundaries of the Roman Empire. See generally, The Founding of Christendom, by Carroll. One of these was St. Thomas, who famously had to touch Jesus’ wounds to declare him “My Lord My God” thus fully realizing who He was. See John 20:28.
Thomas went to India. See here. While he was not successful in converting India to Christianity, there is evidence that he went, and evidence of ancient Christian areas in India. He is said to have come to Taxila in Western Punjab (currently in Pakistan) and evangelized. His efforts to convert the region may have been largely wiped out in later years by Kushan attacks, perhaps around 120 A.D.. See Carroll.
Still, stories persist through history of Christianity in India, a Christianity spread by Thomas, in the centuries after Christ. Indeed, there have even been stories of saints.