The title compound, C14H12N4O2⋅0.5HCl⋅H2O or H(C14H12N4O2)2 +⋅Cl- ⋅2H2O, arose from the unexpected cyclization of isonicotinoyl-N-phenyl hydrazine carbothioamide catalysed by cobalt(II) acetate. The organic molecule is almost planar and a symmetric N⋯H+⋯N hydrogen bond links two of them together, with the H atom lying on a crystallographic twofold axis. The extended structure features N--H⋯O and O--H⋯Cl hydrogen bonds, which generate [001] chains. Weak C--H⋯Cl interactions cross-link the chains. The chloride ion has site symmetry 2. The major contributions to the Hirshfeld surface are from H⋯H (47.1%), Cl⋯H/H⋯Cl (total 10.8%), O⋯H/H⋯O (7.4%) and N⋯H/H⋯N (6.7%) interactions. [ABSTRACT FROM AUTHOR]