Unlikely Partners.
The concept isn't anything new, two opposites being forced to work together as partners grow together and learn to respect each other. Both having strengths where the other is lacking and thereby making an unbeatable team.
For the storyline, as mentioned we have Mel Gibson playing Martin Riggs who is not dealing with the death of his wife and is as a result on the edge emotionally. Hence is willing to put himself in any situation, the more dangerous the better. He is teamed up with family man, by the book and peace loving Roger Murtaugh played by Danny Glover.
When Murtaugh and Riggs are sent to investigate the apparent suicide of a young woman it soon becomes apparent that not all is as it seems. This is also further highlighted when Murtaugh is contacted by a former Vietnam veteran that he served with.
The two of them go back to further question the witness and are almost killed when the house explodes. The kids in the neighbourhood noticed that the "meter man" also had a tattoo exactly like Riggs'. Riggs got his in Vietnam, along with some of the people he served with.
The investigation is now pointing towards a much, much bigger drug importing cartel being run by ex Vietnam veterans with roots back in Vietnam.
Will the two of them survive each other long enough to crack the case, or will the bad guys manage to eliminate them?
I don't believe that Mel or Danny could have been replaced by other actors. They play off each so well. There is plenty of action and also comic relief. This is one of the best films of the 1980's.