3,3-Bis(1H-indol-3-yl)indolin-2-one

In the title compound, C₂₄H₁₇N₃O, the dihedral angles between the planes of the two indole ring systems and the oxindole group are 77.7 (1) and 71.9 (1)°. The mol­ecular packing in the crystal structure is stabilized by an inter­molecular N—H...O hydrogen bond.