The Sandglass is a story of two men whose friendship is put to the test through the 1970s and 1980s, one of Korea's politically tumultuous periods. Park Tae-soo, tough and loyal, grows up to become a gangster and Kang Woo-suk, smart with firm moral values, grows up to become a prosecutor. Yoon Hye-rin, a beautiful and spirited daughter of a very wealthy casino owner, is a classmate of Woo-suk in college. Hye-rin is introduced to Tae-soo via Woo-suk and they subsequently fall in love.