Cosmological simulations show that the growth of galaxies in the early Universe is regulated by the interplay between gas accretion onto dark-matter halos and ejection of matter by stars and active galactic nuclei (AGN). While these processes are routinely described in theoretical works, still little is known from observations on the complex exchanges of mass and energy within the halos of galaxies, where large-scale infall (i.e. accretion) meets outflows (i.e. ejection). Recently, an international team of astronomers was able to probe the halo gas of a massive galaxy system, SMM J02399-0136, using a novel approach. These observations unveiled – for the first time – the infall towards the galaxies of a large mass of diffuse, highly turbulent multiphase gas, pervaded by powerful outflows and more than 10 times larger than the star-forming galaxies.