The potential energy surface for the BeS + H-2 --> SBeH --> HBeSH --> Be + H2S reaction has been investigated by ab initio calculations at the G2(MP2)//MP2/6-31G(d,p) level. The results demonstrate that BeS can readily trap molecular hydrogen. The reaction proceeds by barrierless addition of molecular hydrogen to the Be side of BeS to form the SBeH2 molecular complex bound by 12.4 kcal/mol with respect to the reactants. The complex isomerizes to HBeSH with a low, 5.4 kcal/mol barrier (7.0 kcal/mol below the reactants). The HBeSH molecule is thermodynamically stable and can serve as a storage compound. The energy required for the release of H-2 is calculated to be 55.8 kcal/mol. The BeS + H-2 system has a relatively shallow energy Well of 48.8 kcal/mol at HBeSH for reversible hydrogen storage and a very high barrier of 85.6 kcal/mol for the H2S + Be decomposition. The difference in energy barriers for the release of molecular hydrogen and water is 36.8 kcal/mol, which should make the system of BeS + H-2 highly selective for the reversible hydrogen storage.