Lice, bedbugs, fleas, mites, mosquitoes, ticks, crab lice, which we believed for a moment we had gotten rid of, once again proliferate. Bedbugs invade city centers, lice are doing most well, the Tiger mosquito is on the way to Germany, ticks abound. Why are they back? How can we eliminate rapidly these very unwanted guests? Scientists point the finger at global warming, our too well insulated homes, our lifestyle changes, but also the genetic mutations of these invaders. If some parasites cause minor afflictions, others are vectors of very disabling diseases such as Lyme disease. Embark on a scientific investigation to understand the unexpected return of these bloodsuckers and the potential risks to our health.