The group press on with their tour, and a local servant at a pig farm is killed in the exact same way. The police confiscate the group's passports, so they decide to press on with their tour.
The group are all from an American town called Burlington, where a young girl had been knifed (and de-eyed) a year previously (a fact that seems to have escaped most of their memories). One of their number, Mark Burton, found his wife in an apparently incriminating position-passed out on their lawn, clutching a bloody knife and with a carved-out eye beside her-after that crime, but covered for her. She's now apparently followed him to Barcelona, having passed up an invitation to check herself into a New York mental hospital. Mark's worried that she's the killer, and that she also may have discovered his affair with his secretary Paulette (another tourist).
Apparently fearing that an incriminating picture has been snapped of them, the killer strikes again, dispatching Lisa, a photographer with the group. Before they can thoroughly search her apartment, her lover, Naiba, returns home, forcing the killer to flee. The group press on with their tour. The killer seems rattled by their inability to recover this hypothetical picture, failing to dispatch the next two intended victims-Naiba (again) in hospital, and the group's youngest member, a girl who has a penchant for running off on her own (as do many of the group).
Things come to a head (with its left eye removed) when a reel of film is developed, and an (incredibly clear) incriminating photo is to revealed to have indeed been taken. Naiba sets off to find her friend, a priest, who has pressed on with his touristing, to show him the photo, which shows Paulette creeping along Las Ramblas holding a dagger. Simultaneously, Mark remembers something-Paulette keeps a stash of glass left eyes in a drawer. It turns out that she lost an eye as a child while playing doctor with a friend. Any time she sees someone with the same eye colour-blue-as the friend, she goes a bit mental. She has been trying to frame Mark's wife for the crimes (and the dead girl in Burlington had also been having an affair with him).
It all ends well, and Mark presses on for home, having reconnected with his wife. The grizzled Spanish detective who was racing against time to crack the case before his retirement, watches him go and looks forward to some cracking trout fishing.
A lot of Italian directors stole shots on location, filming without permits. Lenzi and Sergio Martino were probably the leading exponents of this, working quickly with reduced crews to try to attract minimal attention. There are several brilliantly-conceived shots in Eyeball which give the Barcelona locations maximum exposure, before zooming, panning and racking to follow a character (with much looking-down-the-lens action from unwitting bystanders) as they walk through the landscape, before switching to pick out a different character, all within a single take. This is the epitome of efficient filmmaking, showcasing the exotic locations and incorporating character development all at once, allowing the crew to quickly move on with minimal disruption caused. Sergio Martino tended to take a slightly different approach, using handheld cameras to get in close to the action and actors, though the shoot-and-move intention was the same.
Martino and Lenzi were both exceedingly fond of that most 70s of visual tropes-the quick cut to an extreme close of of an object-often flashing or glinting-followed by a swift zoom out. It's a method of scene transition that has gone the way of the zoom lens in general-which is to say, it barely exists-having been supplanted by wipe-style transitions, with an object passing in front of the camera in one scene masking a cut to a similar object passing in a different scene. (Although early Paul Thomas Anderson did often begin with similar close ups, although he used cuts rather than zooms to pull out.) The zoom lens was much beloved of Lenzi, and, combined with his use of racks of focus, and a scope frame, gave his films a distinct look. They had a kind of rough but stylish aesthetic, picking out faces against landscapes in a slightly sub-Leone manner. And Eyeball, with its litany of suspects who are lining up to act is suspicious ways, is a perfect showcase for this approach, with frequent crash zooms into tight close ups.
Another link to Martino comes during the film's climax, when Naiba is trying to escape from a locked castle. She dangles her necklace out a window, hoping to snag it on the key to the front door. A gloved hand appears on the outside and hooks the chain around the key, ensuring that Naiba will fall unwittingly into Paulette's clutches. This is a retread of the moment in Torso where the hand puts the key on Suzy Kendall's newspaper-under-the-door, although Lenzi, perhaps mindful of the moment's coming in the middle of the film's climax (and I'm being generous by reaching for this explanation), rushes through it in a distinctly throwaway manner. Still, the pacing is in keeping with the rest of the film-the second half of Torso would probably occupy no more than five or six minutes of Eyeball's running time.
Returning to the litany of suspects-this is one area where Lenzi does deviate from the norm in some respects. Simply put, everyone is a suspect. Every single character acts, at some point, in an unusual manner, which attracts the suspicion of the other tourists (and us viewers). The possibility of accomplices is also raised, meaning that even those characters who are seemingly alibied due to their being elsewhere when murders occur can thus be considered suspects. There are about 6 potential suspects alive as we reach the climax, giving the audience a flat 16.666666666% chance of guessing correctly. The eventual killer, Paulette, is one of the first characters to have the finger properly pointed at them, after she's spotted cleaning mud from her shoes after the murder of the farmhand girl in a pig pen. All the characters have their moment in the suspect sun, though, with the group displaying an unerring penchant for wandering off on their own, despite knowing that there's a killer in their midst. Their American provenance may have been a neat bit of social commentary on Lenzi's part, for surely no Europeans would behave in such a cavalier, and stupid, fashion (unless they were appearing in another giallo).
Paulette does have one of those moments designed to throw suspicion eleswhere (a 'convenient anomaly') right before the end; when she asks a phone operator to connect her with a top Barcelona lawyer. This makes absolutely zero sense if you think about it, the only possible rationale being to maintain our opinion of her as a loyal secretary out to protect her boss-and lover-'s reputation. Several other plot holes and anomalies abound-Paulette creating a phantom version of Mark's wife running around Barcelona, a city to which the wife had indeed flown (as witness by us in the first scene), unbeknown to Paulette; the incredibly long time which elapses before anyone from Burlington makes a connection between the killings in Spain and that from back home; the motive behind Paulette resuming her murdering after a year (and indeed the exact motive in general), to name but a few. But, all the same, it's not a film which has any pretensions towards high art. It's fun, frivolous and phantastical. And definitely a lot more fun than trout phishing.