Police have registered a case against a man and his parents in Navi Mumbai for allegedly running an investment firm illegally and cheating four investors to the tune of Rs 52.08 lakh by assuring them high returns, an official said on Thursday. The accused, from Uran area in Navi Mumbai, accepted deposits from the four victims between January and April this year while promising to get their money doubled in 30 days, the official from Uran police station said. According to the official, the accused operated the investment business without due permission from the government and the Reserve Bank of India.