One is good, one is "bad", in their lives, because of some reason, they always seem to come across each other.

One is a policeman. One is a "thief". They encounter eachother time after time for various reasons outside work.

HA TSUNG YAM (CHEUNG CHI LAM, JULIAN) is a "thief", who is an undercover policeman the police have carefully infiltrated into a gang whose leader is SUNG PO (YEUN WAH). LAM CHI CHUNG (WONG HE) is a policeman who has sworn to bring PO to justice. YAM sustains a head concussion in an accident, bringing back his memory from his past life. He was previously MO TSUNG, one of the 108 heroes in Water Margin, one of the four greatest Chinese novels, and CHUNG was LAM CHUNG, another hero in the novel. CHUNG finds YAM's story ridiculous and despises him all the more.

YAM pursuse simple love, but CHUNG likes to indulge himself in lust. THey form a love circle with MAN FUNG LIN (LAI CHI, GIGI), who is intrigued and also scared by love, and HONG CHI SIN (YEUNG YI, TAVIA), who is very stubborn in love.

The more YAM fights with CHUNG, the surer he is that CHUNG is LAM CHUNG. He is determined to resurrect CHUNG's memory of his past life in the hope to fight for justice as sworn brothers.