Two Los Angeles police detectives, Martin Riggs and Roger Murtaugh, have developed a strong partnership after their previous brushes with death. Riggs, who has a death wish due to the loss of his wife, has somewhat settled into life again and is known for his unorthodox methods and disregard for his own safety. Murtaugh, a family man close to retirement, is his cautious counterpart trying to avoid further chaos that Riggs often attracts. Despite their differences, they make a formidable team. The pair stumble upon a large-scale criminal operation during a routine investigation when they uncover illegally imported gold Krugerrands which tie back to South African diplomats with immunity.

The investigation into the Krugerrands leads the detectives into a tangled web involving the South African consulate in Los Angeles. They encounter a bureaucrat named Leo Getz, who is part of a money laundering scheme that the diplomats are protecting. As Riggs and Murtaugh delve deeper, they face increasing resistance from the South African diplomats who use their immunity as a shield to avert prosecution. Tensions escalate when the detectives realize that the corruption and criminal activities they are uncovering are only the tip of the iceberg, and the case becomes more dangerous when personal connections to Murtaugh's family emerge, forcing both detectives to protect their own while pursuing justice in the face of international diplomatic complications.