The amino acids synthesis from elementary precursors in abiotic conditions is traditionally described according to the Strecker reaction, thoroughly invoked to justify the observation of amino acids in extraterrestrial samples, and their emergence in the primordial Earth. To this day, however, a quantitative microscopic description of the mechanism, thermodynamics and kinetics of the multi-step Strecker reaction is still lacking. In the present work we tackle this study by adopting a state-of-the-art ab initio computational approach, combining an efficient scheme of exploration of the relevant chemical networks with a rigorous determination of the underlying free energy and transition states. We determine the step-by-step chemical pathway from "Strecker precursors" to glycine in solution, and calculate the corresponding full free energy landscape. Our results agree well with the scarce available experimental data, and complete them, thus providing the first end-to-end study of this complex reaction, a crucial bottleneck for the emergence of life.