The plague raged in Venice from 1348 to 1797, striking in successive deadly waves. Countless votive images produced as "spiritual remedies" brought solace to the faithful terrified of the ongoing scourge. However, in the retables directly related to the plague, we observe the frequent presence of dark clouds. This pattern, which has gone largely unnoticed, is studied here for the first time in detail and associated with contemporary medical theories regarding the aerial spread of the disease. The dark cloud is first examined as an iconographic motif and placed in the context of Venice's health and sanitary situation in the 15th and 16th centuries, as well as the ancient literature on the plague that influenced the humanist thought of the Ve...