As Ben and Al wend their way through the bag-snatching case, they discover drugs hidden in the stolen bag, and their suspicion gradually shifts from the thief (who killed a cop while fleeing the scene) to the suitcase's owner (a smarmy, too-smooth opera singer who has "guilty" written all over him, and yet somehow isn't), and finally to a large crime syndicate, victimizing innocent travelers by turning them into drug mules who unknowingly import product from Asia. Just when the movie seems to be settling into a typical police procedural mold, however, the camera shows us Eli Wallach on a plane, studying grammar. His name is Dancer, and he's an unsophisticated thug trying to learn how to fit into the upper classes; he's with an associate named Julian (the wonderful Robert Keith, a long way here from the tough-guy cop he played in Guys and Dolls just three years earlier), who is older, smartly-dressed, and George Sanders-aloof. And, suddenly, everything changes. In a shift of focus almost as dramatic as the one in Psycho (albeit without the murder), The Lineup reveals itself to be not about cops, but about criminals. Dancer and Julian work for the drug smugglers, and are in town to pick up the goods from a trio of mules, and then deliver them to their unnamed boss. They're professionals with no time for casual conversations, and no patience for the macho bluster of their driver (a young Richard Jaeckel, trying like hell to channel James Dean). The two have worked together so long that Julian can speak for Dancer, and Dancer, the muscle of the team, returns from each pickup with his victims' last words for his partner (Julian's an amateur psychologist, you see, and he's writing a book on dying words). Though he's at first as impenetrable to us as he is the driver, there's nevertheless a threatening edge to Dancer, and Julian reinforces his apparent power by replying with a clipped, warning "No, you haven't," when the driver insists that he "knew a guy like [Dancer] once."
The relationship between Dancer and Julian is a fascinating one, because it's impossible to tell who is in charge. Though the latter is clearly better-educated, older and an orderly thinker who slips easily into the role of organizer and mentor, he seems to be along on the trip almost as a minder, contracted to keep Dancer from going over the edge. That said, however, Julian's guidance is always in the form of suggestions. Even at the tensest, most dangerous moments, he never threatens Dancer, and never takes action against him. Instead, he tries to convince the younger man to do what he's been taught is right. When you can avoid it, for example, you don't kill. "Think," he implores. "Think!"
As The Lineup hurtles towards its climax, Julian's control over Dancer wavers, and when his mentor's suggestions don't lead to the results Dancer expects, all bets are off: He no longer trusts Julian, and has no need to control himself any longer. It's at this point that the true Dancer comes out, and Wallach is allowed to truly bare his teeth as an actor. The film's -- and Dancer's -- tragic conclusion is an inevitable one, and Wallach does impressive work in making his character's break more than just the collapse of a maniac. Even in his wildest, most unhinged moments, Wallach imbues Dancer with fear, confusion and doubt, allowing us to feel sympathy for him to the very end.