3-(2-Hy-droxy-phen-yl)-1-{(E)-[1-(pyrazin-2-yl)ethyl-idene]amino}-thio-urea monohydrate.

In the title compound, C(13)H(13)N(5)OS·H(2)O, the thio-urea mol-ecules closely resemble each other and are approximately planar; the dihedral angles formed between the terminal benzene rings are 7.88 (8) and 7.20 (8)°, respectively. The observed planarity correlates with the presence of bifurcated N-H⋯(O,N) hydrogen bonds. In the crystal, the mol-ecules are connected into supra-molecular double chains via a combination of N-H⋯S (linking the two independent mol-ecules), O-H⋯O and O-H⋯N (linking dimeric aggregates into a supra-molecular chain via hy-droxy-water, water-water and water-pyrazine inter-actions) and O-H⋯S hydrogen bonds (connecting two chains). The chains are further connected by C-H⋯N and C-H⋯S inter-actions.