The title itself, of course, reminds us of "Blow-Up," the 1966 film by Michelangelo Antonioni in which a photographer saw, or thought he saw, a murder—and went mad while obsessively analyzing his photographs of the "crime." Was there a dead body to be found on that fuzzy negative? Was there even such a thing as reality? In "Blow Out," John Travolta plays the character who confronts these questions. He's a sound man for a sleazy Philadelphia B-movie factory. He works on cheap, cynical exploitation films. Late one night, while he's standing on a bridge recording owls and other night sounds, he becomes a witness to an accident. A car has a blowout, swerves off a bridge, and plunges into a river. Travolta plunges in after it, rescues a girl inside (Nancy Allen), and later discovers that the car's drowned driver was a potential presidential candidate. Still later, reviewing his sound recording of the event, Travolta becomes convinced that he can hear a gunshot just before the blowout. Was the accident actually murder? He traces down Nancy Allen, discovers that she was part of a blackmail plot against the candidate, and then comes across the trail of a slimy private eye (Dennis Franz) who wanted to cause a blowout, all right, but didn't figure on anybody getting killed.

The plot thickens beautifully. De Palma doesn't have just a handful of ideas to spin out to feature length. He has an abundance. We meet a gallery of violent characters, including Burke (John Lithgow), a dirty-tricks specialist who seems inspired by G. Gordon Liddy. The original crime is complicated by a series of other murders, designed to lay a false trail and throw the police off the scent of political conspiracy.

Meanwhile, the Travolta character digs deeper. For him, it's a matter of competence, of personal pride. Arguing with a cop about his tapes, Travolta denies that he's just imagining things: "I'm a sound man!" He stumbles across a series of photos of the fatal accident. In a brilliantly crafted sequence, we follow every step as he assembles the film and his recording into a movie of the event, doggedly extracting what seem to be facts from what looks like chaos.

De Palma's visual images in "Blow Out" invite comparison to many Alfred Hitchcock films, and indeed De Palma invited such comparisons when the posters for "Dressed to Kill" described him as "Master of the Macabre." In "Blow Out" there are such Hitchcock hallmarks as a shower scene (played this time for laughs rather than for the chills of "Dressed to Kill"), several grisly murders in unexpected surroundings, violence in public places, and a chase through Philadelphia on the anniversary of the ringing of the Liberty Bell. This last extended chase sequence reminds us of two Hitchcock strategies: His juxtaposition of patriotic images and espionage, as in "North by Northwest" and "Saboteur," and his desperate chases through uncaring crowds, reminders of "Foreign Correspondent" and "Strangers on a Train."