This trilogy follows two Parisian cops: one idealistic and honest, the other experienced and corrupt. In the first film, the corrupt cop persuades his virtuous partner to accept bribes, arguing it's necessary for survival. The honest cop gradually succumbs, but their activities are halted by an internal affairs investigation. The second film sees both using corrupt methods to prove their worth, leading to suspension but later reuniting to take down a criminal gang. The third film depicts their reunion years later, reminiscing on past achievements and lamenting the decline in police honor and camaraderie. The corrupt cop, cynical and jaded by the French justice system's flaws, encourages his partner to adopt a practical approach. The honest cop, initially resistant, becomes disillusioned with the ethical compromises required. The trilogy explores their evolving partnership, from reluctant compliance to moral descent, culminating in a final rejection of the corrupt cop's philosophies.