The 12-membered cyclo-penta-[b]indole ring system in the title compound, C13H13NO2, deviates only slightly from planarity (r.m.s. deviation = 0.051 Å). In the crystal, N-H⋯O and O-H⋯O hydrogen bonds link the mol-ecules into sheets parallel to (100). The five-membered cyclopentanone ring is in slightly distorted envelope conformation with the C atom bearing the hydroxy substituent as the flap.