Thommeray

Honoré Panisse is dying, cheerfully, with friends, wife, and son at his side. He confesses to the priest in front of his friends; he insists that the doctor be truthful. But, he cannot bring himself to tell his son Cesariot that his real father is Marius, the absent son of César, Cesariot's godfather. (imdb)

"Merlusse" is French schoolboy slang for codfish, and M. Blanchard, a professor at a certain lycée, was known to his victims by that name. On Christmas eve, when some twenty of the students--orphans, foreigners or just plain "unwanteds"--had to remain in the boarding school, Merlusse is placed in charge.