Architect Doug Roberts (Paul Newman) returns to San Francisco for the dedication of the Glass Tower, which he designed for developer James Duncan (William Holden). The tower, at 1,688 feet (515 m) tall and 138 stories, is the world's tallest building. During testing, an electrical short starts an undetected fire on the 81st floor just after another such short occurs in the main utility room. Upon learning this Roberts sees the wiring is inadequate and suspects that Roger Simmons (Richard Chamberlain), the electrical subcontractor and Duncan's son-in-law, cut corners. Roberts confronts Simmons, who feigns innocence.
During the dedication ceremony, chief of Public Relations Dan Bigelow (Robert Wagner) turns on all the tower's lights, but Roberts orders them shut off to reduce the load on the electrical system. Smoke is seen on the 81st floor, and the San Francisco Fire Department is summoned. Roberts and engineer Will Giddings (Norman Burton) go to the 81st floor, where Giddings is fatally burned pushing a guard away from the fire. Roberts reports the fire to Duncan, who is courting Senator Gary Parker (Robert Vaughn) for an urban renewal contract and refuses to order an evacuation.
SFFD Battalion Chief Michael O'Hallorhan (Steve McQueen) arrives and forces Duncan to evacuate the guests from the Promenade Room on the 135th floor. Simmons admits to Duncan that he cut corners to bring the project back under budget and suggests other subcontractors did likewise. Fire overtakes the express elevators, killing a group whose elevator stops on the engulfed 81st floor. Bigelow and his mistress Lorrie (Susan Flannery) are killed when fire traps them in the Duncan Enterprises offices on the 65th floor. Lisolette Mueller (Jennifer Jones), a guest being wooed by con man Harlee Claiborne (Fred Astaire) rushes to the 87th floor to check on a deaf mother and her two children. Security Chief Jernigan (OJ Simpson) rescues the mother, but a ruptured gas line explodes and prevents Roberts and the rest of the group from following. The explosion destroys the emergency stairs which they must traverse to reach an exit door leading to a service elevator which can take them to the 134th floor, below the Promenade Room. They await firemen sent to blow up hardened cement blocking access to it.
As firemen begin to bring the fire under control on floor 65, the tower's electrical system fails, deactivating the passenger elevators; O'Hallorhan and other firemen must rappel from a stopped elevator down the elevator shaft to safety.
An attempt at a helicopter rescue fails when high winds cause it to crash and set the roof ablaze. A Navy rescue team attach a breeches buoy between the Promenade Room and the roof of the adjacent 102 story Peerless Building, and rescue a number of guests, including Patty Simmons (Susan Blakely), Duncan's daughter. Roberts rigs a gravity brake on the scenic elevator, allowing one trip down for twelve people, including Roberts' fiancee Susan Franklin (Faye Dunaway), Lisolette and the children saved earlier by her and Roberts' efforts in the stairwell. An explosion near the 110th floor throws Lisolette from the elevator to her death and leaves the elevator hanging by a single cable, but O'Hallorhan rescues the elevator with a Navy helicopter.
As fire reaches the Promenade Room, a group of men led by Simmons attempts to commandeer the breeches buoy which is subsequently destroyed in an explosion, killing Simmons, Senator Parker and several other men. In a last-ditch strategy, O'Hallorhan and Roberts blow up water tanks atop the tower with plastic explosives. Most of the remaining party-goers appear to survive as water rushes through the tower, extinguishing the flames, though several - including the Mayor of San Francisco (Jack Collins) - are killed.
In the tower's lobby Harlee Claiborne, in shock upon hearing of Lisolette's death, is given her cat by Jernigan. Duncan consoles his grieving daughter and hopes that such a tragic disaster will never happen again. Roberts accepts O'Hallorhan's offer of guidance on how to build a fire-safe skyscraper. O'Hallorhan drives away, exhausted.
Paul Newman as Doug Roberts, the Glass Tower architect
Steve McQueen as Michael O'Hallorhan, SFFD 5th Battalion Chief
William Holden as James Duncan, the builder
Faye Dunaway as Susan Franklin, Doug Roberts' fiancée
Fred Astaire as Harlee Claiborne, the con-man who flirts with Mrs. Mueller
Susan Blakely as Patty Duncan Simmons, James Duncan's daughter
Richard Chamberlain as Roger Simmons, the electrical engineer and Duncan's son-in-law
Jennifer Jones as Lisolette Mueller
O. J. Simpson as Harry Jernigan, the chief security officer
Robert Vaughn as U.S. Senator Gary Parker
Robert Wagner as Dan Bigelow, the public relations officer
Susan Flannery as Lorrie
Sheila Matthews Allen as Paula Ramsay
Norman Burton as Will Giddings, electrical engineer
Jack Collins as Mayor Robert "Bob" Ramsay
Don Gordon as Kappy, SFFD Truck Co. 12 fire captain
Felton Perry as Scott, SFFD Engine Co. 4 fireman
Gregory Sierra as Carlos, the bartender
Ernie Orsatti as Mark Powers, SFFD Engine Co. 4 fireman
Dabney Coleman as SFFD Deputy Chief 1
Elizabeth Rogers as Lady in Buoy
Ann Leicester as Guest
Norm Grabowski as Flaker, Navy Air Rescue Chief
Ross Elliott as SFFD Deputy Chief 2
Olan Soule as Johnson
Carlena Gower as Angela Allbright
Mike Lookinland as Phillip Allbright
Carol McEvoy as Mrs. Allbright
Scott Newman as Young fireman
Paul Comi as Tim
George Wallace as Chief officer
Patrick Culliton as technician
William Bassett as Leasing agent
John Crawford as Callahan
Erik Nelson as Wes
Art Balinger as Announcer
Lcdr. Norman Hicks as Pilot
Ltjg. Thomas Karnahan as Co-pilot
Maureen McGovern as Singer at the party (although not listed in the cast credits, her performance is acknowledged in the end titles.)
William Traylor as Bill Harton, security guard (uncredited)
adapted by Stirling Silliphant from a pair of novels, The Tower (1973) by Richard Martin Stern and The Glass Inferno (1974) by Thomas N. Scortia and Frank M. Robinson.