John Nelson Darby writes to Gillett, emphasizing the necessity of faithfulness to Christ amidst trials and the importance of leaning on the Lord during difficult times. He distinguishes between those who are in error due to lack of understanding and those who propagate heresies out of a willful heart, urging a careful approach to teaching and the exercise of spiritual gifts. Darby reflects on the blessings experienced in France and Switzerland, despite his own illness, and expresses a longing to return to England while remaining committed to serving the Lord. He acknowledges his weaknesses and the need for prayer, while encouraging the brethren to remain united in charity and edification.