Set in Eastern China in the mid-19th century Qing Dynasty, Rosy Business tells a story of the mercantile Chiang family and the ambition and jealousy surrounding the issue of who was to own the family business when Chiang Kiu dies. The story surrounds the life of Hong Po-kei, who marries into the Chiang family as Chiang Kiu's fourth wife. She gains ownership of Hing Fung Nin, the family rice shop, and guides the ambitious coolie Chai Kau to rise in the social status ladder.
一場天災,粉碎了本是小家碧玉康寶琦與無錫米王蔣喬的婚約;一次斷糧,滅絕了她全家的性命而淪落為朝廷欽犯。多年來,在寶琦的內心只惦念著當年棄約的蔣喬,總在設法親自求證自己所愛之人絕非無情之士,直至一次偶然的機會,寶琦與蔣喬再遇,得以再續前緣,順利嫁入蔣家成了四姨太。自入門後,寶琦常遭大奶奶殷鳳儀及二少奶彭嬌的無理加害,但她心思慎密、不拘小節,眼觀全局,總是化危為機。喬深明大義,心裡由衷敬佩寶琦的識見及堅持,當他病危離世前決將米業交由她託管,希望她找出最適當的接任人。
這個千斤重任令寶琦腹背受敵,但她不負所託,竭力掌管家業及細心尋覓接任人,終讓她發現外表只管吃喝玩樂的二子蔣必正原是為人正直、重情重義之士,且在米行內極具親和力,寶琦便一面扶植必正上位,一面力擋當年在蔣家受盡折磨,存心報仇的柴九。柴九事事衝著蔣家而來,處處對蔣家不利,二人鬥智鬥力,時而短兵相接,時而拳腳交加,最終強強相對後,二人竟變成惺惺相惜,柴九更因而對寶琦產生傾慕之情..
京城王府廚娘康寶琦(鄧萃雯飾)隨王爺到無錫,只為見曾刻骨銘心的無錫米王蔣喬一面。二人幾經波折,終可再續前緣,蔣喬娶寶琦為四姨太。面對蔣家妻妾互相傾軋,米行風雲暗起,家中各種風波等,寶琦皆以其識見及堅持一一面對。後蔣喬更將當家之權交予寶琦,執掌家業,管治一個米業王國。寶琦肩負千斤重擔,外憂內患之下,仍咬緊牙關,為的是實踐對蔣喬的承諾——為米行尋找合適的接班人,延續蔣喬數十年的基業。