The theme of this book shines through when Christian faces his trials at the Castle of Doubt. Just like every believer, the Christian has not lived up to the glory of God and has betrayed the will of the Lord, making him suffer for his mistakes. While both Christians and Hopefuls begin to doubt the Lord and fear for their lives in the Castle of Doubt, the Lord is as faithful as ever and provides the two Pilgrims with a way out of the tortuous situation.