The film opens in Saigon at the height of the Vietnam War. John Converse, a disillusioned war correspondent, approaches Ray Hicks, a merchant marine sailor and acquaintance of Converse from the U.S., for help in smuggling a large quantity of heroin from Vietnam to San Francisco, where he will exchange the drugs for payment with Converse's wife Marge, who has become addicted to Dilaudid. When Hicks gets back to the U.S. and discovers he is being followed by thugs connected either to Converse or his suppliers, he goes on the run with Marge and the heroin, and eventually they are pursued by corrupt DEA Agent Antheil, who initially set the deal in motion. As Marge is separated from her supply of Dilaudid, she experiences withdrawal, and Hicks decides to help wean her off her addiction by using the heroin. Hicks also attempts to find another buyer for the heroin before his pursuers can catch up to him.
The film is based on Robert Stone's novel Dog Soldiers, which won the National Book Award for fiction in 1975. For its original US theatrical release it was re-titled Who'll Stop the Rain, after the Creedence Clearwater Revival song, which features prominently on the film's soundtrack. The film was released as Dog Soldiers in several places. Some copies of the DVD of Who'll Stop the Rain actually contain prints titled Dog Soldiers. Stone based the character of Ray Hicks on Beat writerNeal Cassady, with whom Stone became acquainted through novelist Ken Kesey, a graduate school classmate of Stone's at Stanford University. Hicks' death scene on the railroad tracks at the film's conclusion is directly based on Cassady's death along a railroad track outside of San Miguel de Allende, Mexico, in 1968. The hippie commune setting, where lights and stereo speakers placed throughout the woods are utilized in Hicks' escape plan, is partially based on Kesey's home in La Honda, California, where Kesey and his friends — known as the Merry Pranksters — famously wired the surrounding woods with lights and sound equipment to enhance their experiments with LSD. The Saigon scenes were filmed on a set in Mexico. There was a casting advertisement in Mexico City for people of any Asian background to represent the Vietnamese.
