Black Mail is a 1973 Bollywood thriller film directed by Vijay Anand. The film stars Dharmendra, Raakhee, Madan Puri, and Shatrughan Sinha.
Dr. Khurana, an eccentric scientist, discovers a formula to generate electricity from sun light. This discovery makes him very popular, and his formula very much in demand, while local businessman, Mr. Mehta, feels threatened - as this may means losses and eventual bankruptcy. Mehta and his associate, Jeevan, who is also his daughter's (Asha) sweetheart, connive a plan to get Asha married to Dr. Khurana's nephew, Kailash Gupta; inherit part of the estate as well as the business along with the formula; and thereby eliminate their potential bankruptcy. Their only problem is Asha, who may not cooperate. - This uses material from the Wikipedia article Black Mail, which is released under the Creative Commons Attribution-Share-Alike License 3.0.