Every year in France, tens of thousands of people are bitten by ticks. Some will go on to develop severe and debilitating symptoms because of a particular bacterium: Borrelia burgdorferi. These patients have Lyme Disease, which is difficult to diagnose and treat. This documentary tracks the movement of ticks in the Grand-Est region of France in an attempt to explain the imbalances that have led to an increase in tick numbers and a corresponding rise in cases of Lyme disease. Can these phenomena also be characteristic of other diseases, such as Dengue Fever, Chikungunya or Zika?