This paper proposes a novel data hiding technique in image using Kirsch operator, which has unique feature to find maximum edge strength in different orientations. Depending on a threshold value for the Kirsch operator and the intensity value of each pixel of cover image, a scale with 3 ranges would be created. This scale is the basis for choosing flexible, i.e., 2, 3, or 4 LSB replacements for steganographic encoding. The threshold value is sharable to intended receiver as a key and if appropriate reverse approach is taken, secret image can be successfully retrieved without any data loss. This work has been carried on different grayscale images, maximum payload has been calculated, PSNR and SSIM values are measured to get satisfactory result of quality. To ensure un-detectability, Bhattacharyya distance has been calculated and for robustness test, RS steganalysis attack has been performed. © Springer Nature Singapore Pte Ltd. 2019.