We consider a Poissonian distribution of particles performing independent simple random walks. Simultaneously, on top of this system, a random walker evolves with a drift to the right when it is on top of (at least) a particle, to the left when it is on an empty site. We obtain a LLN, CLT and large deviation bounds in high and low density. Joint work with Marcelo Hilario, Renato dos Santos, Vladas Sidoravicius, Augusto Teixeira.