The paper investigates the relationship between galaxy star formation rate (SFR) and local galaxy density in the distant universe, specifically at redshifts $z \sim 1$. Using ultradeep imaging from the *Spitzer* MIPS camera, the authors determine the contribution of obscured light to the SFR of galaxies over the redshift range $0.8 \leq z \leq 1.2$. Accurate galaxy densities are measured using a large sample of spectroscopic redshifts with high completeness. Morphology and stellar masses are derived from deep HST-ACS imaging and ground-based data. The results show that the star formation-density relation observed in the local universe is reversed at $z \sim 1$: the average SFR of galaxies increases with local galaxy density when the universe was less than half its present age. This reversal is not predicted by hierarchical galaxy formation models, which suggest such a reversal should occur only at earlier epochs ($z > 2$) and at a lower level. The authors also present a structure at $z \sim 1.016$ containing X-ray-traced galaxy concentrations that will eventually merge into a Virgo-like cluster, illustrating how the individual SFR of galaxies increases with density. The SFR of $z \sim 1$ galaxies correlates with stellar mass, suggesting that mass plays a role in the observed star formation-density trend. However, the specific SFR ($\equiv$SFR/M$_*$) decreases with stellar mass while it increases with galaxy density, indicating that the environment directly affects the star formation activity of galaxies. Major mergers do not appear to be the primary cause of this effect, as nearly half of the luminous infrared galaxies ($\geq 11 \leq \log _{10}(L_{\text{IR}}) \leq 12$) at $z \sim 1$ present spiral morphologies. The findings constrain the influence of large-scale structure formation on the star formation history of galaxies. Reproducing the SFR-density relation at $z \sim 1$ is a new challenge for models, requiring a balance between mass assembly through mergers and in-situ star formation at early epochs.The paper investigates the relationship between galaxy star formation rate (SFR) and local galaxy density in the distant universe, specifically at redshifts $z \sim 1$. Using ultradeep imaging from the *Spitzer* MIPS camera, the authors determine the contribution of obscured light to the SFR of galaxies over the redshift range $0.8 \leq z \leq 1.2$. Accurate galaxy densities are measured using a large sample of spectroscopic redshifts with high completeness. Morphology and stellar masses are derived from deep HST-ACS imaging and ground-based data. The results show that the star formation-density relation observed in the local universe is reversed at $z \sim 1$: the average SFR of galaxies increases with local galaxy density when the universe was less than half its present age. This reversal is not predicted by hierarchical galaxy formation models, which suggest such a reversal should occur only at earlier epochs ($z > 2$) and at a lower level. The authors also present a structure at $z \sim 1.016$ containing X-ray-traced galaxy concentrations that will eventually merge into a Virgo-like cluster, illustrating how the individual SFR of galaxies increases with density. The SFR of $z \sim 1$ galaxies correlates with stellar mass, suggesting that mass plays a role in the observed star formation-density trend. However, the specific SFR ($\equiv$SFR/M$_*$) decreases with stellar mass while it increases with galaxy density, indicating that the environment directly affects the star formation activity of galaxies. Major mergers do not appear to be the primary cause of this effect, as nearly half of the luminous infrared galaxies ($\geq 11 \leq \log _{10}(L_{\text{IR}}) \leq 12$) at $z \sim 1$ present spiral morphologies. The findings constrain the influence of large-scale structure formation on the star formation history of galaxies. Reproducing the SFR-density relation at $z \sim 1$ is a new challenge for models, requiring a balance between mass assembly through mergers and in-situ star formation at early epochs.