The film opens with an American engineer named Harry Burck (Harmon) being kidnapped by rebels in Colombia. Harry is there to help open a new water pipeline for his company and gets caught up in the action when a diplomat who is on hand for the pipe's unveiling is kidnapped. Word reaches back to Harry's brother Corey (Schoeffling) and his friends Bob (Wilson), cocaine addict Spence (Frey) and Kurt (Rossovich), who were all awaiting his return home to Illinois. The men, who all work together at the same factory, learn that Harry was kidnapped by a druglord named Carlos Ochobar. Corey and Bob travel to Washington only to learn that the U.S. Government is not going to mount any rescue attempt for Harry. We learn that the men (and everyone in the town) hold Harry in high regard. Kurt reminds his friends that they all owe Harry something, so he says their only choice is to rescue him themselves. Despite some resistance and skepticism from Kurt and Spence, all the men eventually agree to go. Before heading to Colombia, they enlist the financial help of a local car salesman named Jack (Busey), who insists on going along, and the military expertise of a decorated no-nonsense mercenary named Norman Shrike (Duvall).
Once in Colombia, they encounter resistance from the start, both from local officials and from the U.S. Government. They eventually land in jail after being set up by one of Shrike's contacts who was supposedly going to supply them with weapons. They are handed over to the U.S. in order to be put on a plane back home. They escape the plane at the last minute, but Kurt decides he has had enough and he stays behind. They continue on without him and eventually Shrike is killed in a firefight while saving one of the men's lives. The group ventures on with the help of a local woman and they eventually find Ochobar's hideout. In the ensuing shootout with Ochobar's men, Jack is killed. The group is able to save Harry and then escape, destroying Ochobar's camp in the process.
Almost all of the ensemble cast was famous at the time of the movie, and it is rare that a film with so many known actors is so forgotten. At the time of the movie's release in 1986, Harmon was fresh off of St. Elsewhere, Schoeffling was two years removed from Sixteen Candles, Wilson had just done Back to the Future, Rossovich was starring in Top Gun and Frey was famous for being a member of the Eagles and his recent solo work such as the smash hit "You Belong to the City". Both Duvall and Busey were well-established at the time and screen legend Ben Johnson also appeared in the film, playing Mr. Burck. Despite its impressive cast, Let's Get Harry is a film that is remembered for little except Rosenberg's decision to remove his name from the credits. This is due to significant reediting and additional shooting that occurred after principal production concluded. In the director's cut of the film, Mark Harmon doesn't make an appearance of any kind until the final rescue sequence. Prior to planned release, Harmon's public popularity grew dramatically due to his work on "St. Elsewhere" and the producers wanted to make Harmon more at the center of the story over Rosenberg's objection. The shooting of additional footage featuring Harmon's abduction and being held as a hostage brought about the "Alan Smithee" disignation.
In general the film is viewed as poorly-written and executed. Many of the scenes are rather unrealistic, most notably the final assault on Ochobar's camp. The men, none of whom have had any training, are able to kill dozens of Ochobar's men and destroy his camp with improvised bombs.
Let's Get Harry was one of a number of 1980s films that centered on civilians partaking in hostage rescues without the help of the U.S. Government. Other similar films that were released around the same time were Uncommon Valor, Rambo: First Blood Part II, Iron Eagle, and The Rescue.