Visual Cryptography Scheme (VCS) is a cryptographic technique which can hide image based secrets. Even though VCS has the major advantage that the decoding can be done with the help of Human Visual System (HVS), yet it does not provide sufficient reconstruction quality. Hence, Two in One Image Secret Sharing Scheme (TiOISSS) is used which provides two decoding phases. However, the existing TiOISSS method has several limitations. In this work, a Modified TiOISSS is proposed in which an adaptive threshold is used for halftoning, which changes depending on the nature of the pixels present in image. By this, the quality of reconstructed secret image is improved in the first decoding stage compared to the existing scheme. In addition, the security is also enhanced by pixel and bit level permutation with a 64 bit key and embedding the key in Gray VCS shadows. To verify the authenticity of the image, a secret message is also embedded in the shadows. Security analysis shows that the Modified TiOISSS is robust to Brute Force and Man-in-Middle attacks.