Two just-graduated officers from Massachusetts State Police Academy follow opposite sides of the law: William Costigan is assigned to work undercover with the Irish mobster Frank Costello to get evidences to arrest him. His true identity is only known by his superiors Dignam and Oliver Queenan. The protégée of Costello, Colin Sullivan, is promoted in the Massachusetts State Police and is the informer of Costello. Each police officer gives his best effort trying to disclose the identity of the other "rat".
Two hundred and fifty years in the future, life as we know it is threatened by the arrival of Evil. Only the fifth element can stop the Evil from extinguishing life, as it tries to do every five thousand years. She is helped by ex-soldier, current-cab-driver, Korben Dallas, who is, in turn, helped by Prince/Arsenio clone, Ruby Rhod. Unfortunately, Evil is being assisted by Mr. Zorg, who seeks to profit from the chaos that Evil will bring, and his alien mercenaries.
Six criminals, who are strangers to each other, are hired by a crime boss Joe Cabot to carry out a diamond robbery. Right at the outset, they are given false names with an intention that they won't get too close and concentrate on the job instead. They are completely sure that the robbery is going to be a success. But when the police show up right at the time and the site of the robbery, panic spreads amongst the group members and one of them is killed in the subsequent shootout along with a few policemen and civilians. When the remaining people assemble at the premeditated rendezvous point (a warehouse), they begin to suspect that one of them is an undercover cop.