The structure and vibrational spectra of a marginally stable conformer of glycine (usually referred to as VIp or ttc) recently detected in low-temperature matrices have been characterized by a state-of-the-art computational approach allowing an overall quality for bond distances, rotational constants, conformational enthalpies and vibrational frequencies well within the chemical accuracy. The high accuracy of the computational results allows us to draw a fully consistent interpretation of the available experimental data and to obtain a more complete characterization of an elusive glycine conformer.