In 1794 he was conscripted into the army, but managed to obtain his freedom with the help of friends and received his final discharge from Napoleon's wife Joséphine de Beauharnais.

In 1816 he moved to Rouen, a large city by the standards of the time, where he hoped to find work as an artist to support his wife and seven children.

[3] Surrounded by buildings and ruins from the Middle Ages, Langlois became a prolific creator of drawings in the gothic style, depicting the supernatural world of devils and sorcerers based on ancient legends and embellished by his imagination.

[4] Langlois devoted himself to the study and preservation of his Norman heritage, and gradually became well known for his writings and illustrations on historical subjects.

[7] In the bombardment of the cathedral in April and June 1944 during World War II some of the stalls and misericords were destroyed and others badly damaged.

Langlois's book, illustrated by drawings made by his daughter, provides the main source of information on the destroyed stalls and misericords.

[9] During a period of hardship Langlois made a sketch of a piece of furniture for a manufacturer who promised to pay 500 francs for a detailed drawing.

[4] His experiences during the revolution and subsequent Napoleonic Wars, which continued until 1815, reinforced Langlois' Christian and anti-revolutionary beliefs, and these are evident in his work.