Eddie Albert and Diana Muldaur co-star. The film also features Roger E. Mosley as a pimp and police snitch, Clu Gulager as a corrupt police detective, Colleen Dewhurst as a cocaine addict and Al Lettieri in one of his final roles, as the most visible villain of the film, the drug king Santiago.
One of Wayne's famous lines from this movie is delivered after his character is trapped inside his car after it was crushed between two large trucks. He says to one of the reporting officers "I'm up to my butt in gas."
It is just before dawn in Seattle. A man dons dark glasses and gloves and loads a 9mm silenced automatic handgun. He drives into town, where he shoots a policeman (Officer Philip Forsell; in the film the character is identified only as Hyatt) on his beat, then drives to a police impound yard and shoots the officer on duty (dialogue identifies him as Wally Johnson). At a luncheonette, as he washes his hands, he momentarily flashes a police badge belonging to Detective Sgt. Stan Boyle (William Bryant). When a car pulls up, Boyle goes outside and gives the driver a satchel containing the 9mm and proceeds to his own car – but is shot in the back by the unseen driver.
Seattle Police Department, and the head of the homicide investigation, Captain Edward Kosterman (Eddie Albert), believe the shootings are the work of street militants; Kosterman orders an immediate dragnet.
Elsewhere, Detective Lieutenant Lon "McQ" McHugh (Wayne) escapes an attempt on his life by a professional hit man named Samuels. McQ had been woken minutes before by a phone call to him on his boat, telling him of the shootings of his longtime partner and the two other police officers.
Because he and Boyle had been investigating drug trafficking in the city, McQ is convinced from the start that the target of their investigation, local shipping magnate and known drug dealer Manny Santiago (Al Lettieri), is responsible for the shootings.
Despite a warning from Captain Kosterman to leave the investigation to the department, McQ, after talking with Boyle's wife Lois (Diana Muldaur), gets behind the wheel of his personal Pontiac Firebird car and begins tailing Santiago. After seeing a TV news report that Boyle has died of his injuries, he rages after Santiago and beats him viciously in a men's room.
When confined to desk duty by Kosterman, McQ angrily resigns, despite pleading from fellow detective Franklyn Toms (Clu Gulager). Continuing to investigate the case through a partnership with local private eye "Pinky" Farrell (David Huddleston), McQ learns that Santiago has assembled a heist team to steal the confiscated heroin and cocaine from the police department's evidence vault. The drugs are normally held by the department until turned over to the State Attorney General's Office for disposal. Santiago's men steal the drugs just as the narcotics are about to be burned in an incinerator. McQ pursues Santiago's men, but they escape. After getting a much harsher warning from the increasingly exasperated Kosterman, McQ is informed by Kosterman that the approval for McQ's application for a private investigator's license is being placed on hold. Kosterman relieves McQ of his Colt revolver. McQ goes to a local gun store and acquires for himself a Browning Hi-Power 9mm pistol and a MAC-10 9mm submachine gun.
McQ breaks into Santiago's office but is cornered by Santiago and his men. Santiago reveals that the drugs his men stole had turned out to be only powdered sugar. The real drugs, from hundreds of major and minor cases and investigations, had been carefully, over a period of years, replaced with the sugar. Obviously this could not have been done without extensive corruption throughout the department. McQ also realizes that Santiago was not responsible for Stan Boyle's death. Knowing McQ is not a threat, Santiago lets him go – though he beats him brutally as payback for the earlier assault.
McQ's investigation leads to the shooting of one of his sources, bartender Myra (Colleen Dewhurst), and another attempt on McQ's life, in which his Firebird is crushed between two huge trucks. McQ escapes, but when he examines the wreckage he finally discovers who is behind the killings of Boyle and two other officers, and also who is behind the theft of drugs from the police, leading to a climactic chase and shootout at a beach with Santiago and his men.John Wayne as Det. Lt. Lon "McQ" McHugh
Eddie Albert as Capt. Edward Kosterman
Diana Muldaur as Lois
Colleen Dewhurst as Myra
Clu Gulager as Toms
David Huddleston as "Pinky" Farrell
Jim Watkins as J.C.
Al Lettieri as Manny Santiago
Julie Adams as Elaine
Roger E. Mosley as Rosey
William Bryant as Sgt. Stan Boyle
Richard Kelton as Radical
Richard Eastham as Walter Forrester
The movie was filmed on location in Seattle, Aberdeen, Washington, and at the Quinault Indian Reservation in Washington.
Hal Needham, the legendary maverick stunt car driver, performed the very first car stunt utilizing a black powder cannon charge to help flip the car without ramps in this film. The climatic car chase seen on the beach, near the end of the movie, was first practiced on the back lots of LA, and on the 2nd practice run, that was unknowingly overcharged, Needham was nearly killed. Gary McLarty then performed the dynamic stunt flawlessly (and injury free) for the film.
While filming the beach scenes in 1973, the crew stayed at the Polynesian Hotel (The "Poly") in Ocean Shores.
A novelization of McQ, written by Alexander Edwards, was published in 1974 by Warner Books (ISBN 978-0446764940). The novel was written before the filming of the movie and consequent script changes. There are subtle differences, such as McQ living in an apartment rather than a boat. And the gun used by McQ in the climax is a Mauser in the book instead of the grander Mac 10 automatic machine gun used in the movie. Some scenes are deleted or modified, but on the whole the book is true to the movie in both dialogue and plot.
Nora Sayre of The New York Times thought the movie was slow: "In this wildly undramatic picture, music and gunshots have to provide the gumption that the acting lacks. Surely Mr. Wayne should stick to Westerns: he's simply too slow to play any kind of policeman. Horseless in the streets of Seattle, he looks as though he needs a shot of sand."
James M. Tate of Cult Film Freaks said the movie has a film noir quality: "Director John Sturges was, like Wayne, best known for making Westerns, a genre McQ borrows from with the maverick loner verses an eclectic string of feisty (and often sneaky) antagonists, each with their own lethal agenda, sometimes even coming out of the woodwork with guns blazing. But with the cool looking MAC-10 submachine gun and a snaky trail pitting one man against shadowy odds, this is really a modern Noir thriller providing a chance to see the American icon grittier, and often more vulnerable, than ever before: at least in a modern setting."