Based on the 1965 novel Fruit of the Poppy by Robert Wilder, it was released in the UK as The Heroin Gang and in Australia as The Secret File of Sol Madrid.

Half a million dollars is stolen from the mafia by small-time crook Harry Mitchell, who splits it with girlfriend Stacey Woodward and takes off for Acapulco.

Sol Madrid, an undercover narc, is out to find Harry first, hoping to persuade him to testify against organized crime in court.

Things get complicated in Mexico, where a heroin dealer named Dietrich is engaged in criminal activity while Mexican law official Jalisco is on the case.

The film score was composed by Lalo Schifrin and the soundtrack album was released on the MGM label in 1968.