«The black spot» is a piece of cloth or paper marked black on one side and scribbled with a threat on the other. The small artifact is used by pirates to communicate with each other in Robert Louis Stevenson’s novel «Treasure Island» (1883). If Stevenson invented «the black spot», we owe Théo Varlet (1878-1938) the creation of «la tache noire» for the French translation of 1920. The three words in French, repeated by the printing press, are the starting point of an investigation on Théo Varlet, initiated in a personal library and completed by the side of a well in the south of France. Backed by documents, the story examines this adjustment in the act of translating that can lead to disaster.