After a botched attempt to nab a drug smuggler in a parking garage, police detectives Ho Ting-Bon (Yun-Fat Chow) and Cheong Yan (Fong Liu) accidentally cause a runaway car to hit a young woman, Kwong Sun (Joey Wang), who is in the city illegally. Sun then fakes amnesia in order to protect her illegal identity, and is put-up for several nights by Bon. While Sun struggles to find her identity papers in Hong Kong and relatives to take her in, Bon feels compelled to let her stay in his home. However, Sun can only fake her amnesia for so long.