Kashmakash (1973)

Kashmakash is a thriller where Feroz Khan, Shatrughan Sinha and Rekha are playing stellar roles. Satish Gupta and Seeta are a happily married couple till one day, on the insistence of his friend ManMohan, Satish visits Sapna for an illicit rendezvous at her hotel where she performs as a cabaret artist, and there he sees her in her bathtub, from wherein she leads him to her bed. Before anything can happen, Sapna is ruthlessly murdered in the dark with a knife. Satish rushes out of her room, but is caught red handed on the stairs, by a private detective I. S. Johar, who plays himself in the movie, and who keeps tabs on influential people to nab their illicit dealings to blackmail them.