The Church in Thyatira

Much like the followers of Jesus in Pergamum, the church in Thyatira was doing a great work. Jesus was impressed and commended them on their work, love, faith, service, patience, and even going beyond their beginning works as a church. But just like the church in Pergamum, they not only opened a back door, but they left it open to such an extent that the enemy came into their church. What was the door that they opened, and what was to become of this faithful church?