 Abstract molecular polaritons are hybrid light matter states that emerge when a molecular transition strongly interacts with photons in a resonator. At optical frequencies, this interaction unlocks a way to explore and control new chemical phenomena at the nanoscale. Achieving such control at ultra-fast time scales, however, is an outstanding challenge, as it requires a deep understanding of the dynamics of the collectively coupled molecular excitation and the light modes. Here, we investigate the dynamics of collective polariton states, realized by coupling molecular photos which is to optically an isotropic plasmonic nano-antenors. Pump probe experiments reveal an ultra-fast collapse of polaritons to pew molecular transition triggered by femtosecond pulse excitation at room temperature. Through a synergistic combination of experiments and quantum mechanical modeling, we show that the response of the system is governed by intramolecular dynamics, occurring one order of magnitude faster with respect to the uncoupled excited molecule relaxation to the ground state. This article was authored by Joel Cutruff, Marco Rominelli, Esther Ban Pedro Azevil Almanzo, and others. We are article.tv, links in the description below.