At the opening party of a colossal, but poorly constructed, office building, a massive fire breaks out that threatens to destroy the tower and everyone in it.
- John Guillermin
Duncan Enterprises, an architectural and construction empire, is readying the dedication of The Glass Tower, the world's tallest skyscrapper, located in San Francisco. Amid the activities of James Duncan and his chief architect Douglas Roberts, a circuit breaker blows in the building's main utility room - and unknown to all the surge blows another breaker that lights materials in a storage closet on fire. The electrical snafu forces Roberts to cut short a planned vacation with his fiance Susan Franklin and to confront Roger Simmons, the firm's chief electrical specialist who oversaw installation of the wiring. As the dedication party proceeds on schedule, Roberts finds the building's wiring is in worse shape than he could have expected, and it all blows up when the burning storage closet suddenly erupts into the corridors. The fire spreads with such speed that the entire San Francisco fire department must be called in, lead by Batallion Chief Michael O'Halloran, who expresses his distaste for skyscrappers to Roberts because the department can't easily combat a fire above the seventh floor. The two men still must work together, as 300 guests are trapped in the spacious Promenade room at the building's summit - and the fire continues to spread and set off gas explosions, to the point that the only chance to extinguish the fire may well kill the trapped partiers atop the Tower.