The Cat o' Nine Tails

As the sun sets over the city, a mysterious figure slips into the Terzi Medical Institute, leaving behind no apparent evidence of their presence - or so it seems. For Dr. Calabresi, one of the institution's esteemed physicians, has stumbled upon a crucial truth: he knows the identity of the intruder and the motivations driving them. His attempt to leverage this knowledge leads him down a treacherous path, ultimately ending in his untimely demise at the hands of the very person he sought to blackmail. A paparazzo happens to capture Calabresi's fall on camera, but the killer remains shrouded in shadows.

In the days that follow, investigative journalist Carlo Giordani delves deeper into the enigma surrounding Calabresi's death, crafting an article that sparks a flurry of activity. Franco "Cookie" Arnò, a veteran reporter now confined to his wheelchair due to blindness, and his niece Lori, are drawn into the maelstrom when they visit Carlo at his office. Franco's sharp instincts lead him to suspect that someone has tampered with the photo evidence, and further investigation confirms this notion. The photographer's untimely demise at the hands of an unseen assailant only adds to the sense of urgency.

As Carlo and Franco work in tandem to unravel the tangled threads of the case, they identify nine leads worth pursuing: the five remaining Institute scientists - Mombelli, Esson, Casoni, Braun, and director Terzi - Anna Terzi, Bianca Merusi, the original break-in, and the missing photographs. Their conversation is punctuated by wry humor as they liken their investigation to a cat o' nine tails, with each strand representing a potential clue waiting to be untangled.

Carlo's interview with Anna Terzi yields revealing insights into the Institute's research on "XYY syndrome," which suggests that individuals bearing this unique genetic trait are more prone to criminal behavior. Meanwhile, Franco and Lori pay a visit to Bianca Merusi, Calabresi's bereaved fiancée, who proves reticent in sharing any additional information. However, Lori notices Bianca nervously fidgeting with a locket as she speaks, an action that sparks Franco's curiosity.

As night falls, Bianca finds herself at the center of a sinister plot when she breaks into Calabresi's car and discovers a cryptic note detailing the identity of their mutual killer. She conceals this vital information within her locket before returning to her apartment, where the killer lies in wait. Despite receiving a chilling warning from the perpetrator, Carlo and Franco remain undeterred, driven by their determination to uncover the truth.

In the days that follow, they delve deeper into the case, interviewing various Institute personnel. Dr. Mombelli reveals that all researchers submitted blood samples for analysis as part of the XYY research project, while Dr. Casoni speculates about the potential for such testing to become a tool in crime prevention. That night, both Carlo and Franco narrowly avoid separate attempts on their lives. As they regroup and reassess their strategy, they learn that Dr. Braun has gone missing, prompting suspicions of foul play. In a desperate bid to uncover the truth, Carlo pays a visit to his boyfriend's residence, only to discover the unfortunate doctor stabbed to death in a gruesome tableau.

As Franco shares his theory with Carlo, the duo hypothesizes that Bianca's demise was a calculated move by the killer, who must have suspected she possessed incriminating evidence. The investigation leads them to recall Lori's fleeting mention of Bianca's treasured locket, sparking an intense curiosity about its contents. With the crypt door finally creaking open, they uncover Bianca's coffin and, inside the locket, a folded note that hints at secrets yet to be unearthed. Just as Franco and Carlo are on the verge of unraveling the mystery, the killer intervenes, slamming the crypt door shut and pouncing on Franco outside. The note is seized, but Franco retaliates by plunging his sword cane into the attacker's flesh, sending them fleeing.

The killer, still reeling from Franco's counterattack, issues a chilling ultimatum: he has taken Lori hostage and will execute her unless they desist from investigating. Realizing that the killer would eliminate Lori regardless, Franco, Carlo, and the authorities converge on the Terzi Institute in a desperate bid to rescue the captive Lori. However, their search proves futile, with only Carlo's keen instincts leading him to track down the blood-soaked trail of evidence to the rooftop. There, he finds Casoni, the perpetrator, poised to strike a bound and gagged Lori. With split-second reflexes, Carlo leaps into harm's way, absorbing a stab wound in his shoulder as the police arrive to chase down Casoni.

As Franco closes in on the killer, his fury is fueled by Casoni's lies about Lori's fate. Enraged, Franco unleashes his cane blade, pinning Casoni against the skylight, before sending him plummeting down an elevator shaft to meet a gruesome demise. With Casoni's defeated form vanishing into the depths below, a freed Lori's anguished cry for help pierces the night air, as Franco stands poised to reunite with his beloved.