Fauchelevant was a business rival of Valjean and was later forced to earn money as a carter.
One day, his horse broke two of its legs, and Fauchelevant fell underneath his cart and was stuck, which was sinking into the mud. Valjean, being exceptionally strong, crawled under the cart and lifted it off Fauchelevant, saving him from from being crushed to death. After Fauchelevant recovered, Valjean procured him a job as a gardener at the Petit Picpus convent.
While escaping from Javert with Cosette, Valjean arrives at the same convent by climbing over the wall, where Fauchelevant recognizes him. Feeling indebted to Valjean, he housed him and Cosette. However, they could not risk being found after sneaking in, so they needed to exit the convent and be officially admitted. At the same time, one of the nuns recently died and wanted to be buried under the altar, but it was illegal to keep bodies. Fauchelevant smuggled Valjean out of the convent in the coffin, under the guise of the dead nun, and Cosette in a basket. They were both later admitted into the convent, Valjean posing as Fauchelevant's brother Ultimus (who had died), and Cosette as Ultimus' granddaughter.