As Juliet Forrest, the daughter of the renowned scientist and cheesemaker John Forrest, implores private investigator Rigby Reardon to unravel the enigma surrounding her father's suspicious passing, an intricate web of intrigue begins to unfold. Upon inspecting Dr. Forrest's laboratory, Rigby stumbles upon two mysterious lists entitled "Friends of Carlotta" (FOC) and "Enemies of Carlotta" (EOC), alongside an autographed image of the alluring songstress Kitty Collins, whose name is found among the listed friends. The tension escalates rapidly when a gunman unexpectedly appears, firing at Rigby and making off with the lists, setting the stage for a gripping investigation.
Hobbling his way to Juliet's home, Rigby receives her medical care as she expertly extracts the bullet from his arm. Their dialogue unveils a peculiar note left by Dr. Forrest for his brother-in-law, Sam Hastings, which points to a strange gift—a dollar bill featuring FOC names, including Kitty and her partner, Swede Anderson. This discovery triggers a chain of events leading Rigby to seek out Sam, only to find the same dollar bill, now marked with FOC names, thereby deepening the mysteries surrounding the case.
In his quest for the truth, Rigby approaches Kitty, and when he inquires about her connection to Carlotta, she hastily makes her exit. Undaunted, he follows her to a nearby diner, where she carelessly drops her brooch into her soup. Capitalizing on this opportunity, Rigby retrieves the brooch, which reveals an EOC list with all names crossed out except for that of Swede Anderson. His visit to Swede ends tragically as Rigby is shot in the same arm again, compelling Juliet to intervene once more.
As Rigby recuperates, he reaches out to his mentor, the legendary Philip Marlowe, in search of clarity within the convoluted case. Juliet provides him with a key from Dr. Forrest's desk along with a key to train station locker 1936. Marlowe utilizes these clues to explore potential links between the EOC list and a series of unresolved murders.
Continuing his investigation, Rigby ventures to the train station locker, where he finds F.X. Huberman, whose name was on one of the lists, engaged in a lively gathering. As they exchange flirtatious banter, Rigby gradually finds himself inebriated, only to discover that his drink has been spiked and the locker key has been stolen by Huberman. After this encounter, Juliet arrives with the devastating news of Sam Hastings' demise—a fatal fall from a window while attempting to grasp a whiskey bottle.
Furthermore, Marlowe imparts crucial information regarding Walter Neff, the mysterious owner of the Immer Essen cruise ship, which had recently been mentioned in an article by The New York Times. This new knowledge ignites further investigation into Neff's unscrupulous activities, including his unusual practice of seeking out blondes in supermarkets. As Rigby's relentless pursuit for truth continues, the stakes become perilously high, causing the boundaries between truth and illusion to blur.
In a twist of audacity, Rigby dons a blonde wig in an effort to blend in with Neff, and cunningly drugs him to procure a passenger manifest from the Immer Essen, mirroring an Enemy of the Crown list, allegedly containing details about the incarcerated captain Cody Jarrett, known for only communicating with his mother. Rigby's strategy takes a dangerous turn as he attempts to impersonate Jarrett's mother, trying to win the captain’s trust with cautionary tales about the FOC. However, when his plan falters, he shifts tactics to masquerade as a prisoner, only to face Jarrett's swift and deadly response—another bullet that forces Rigby to the ground.
As Juliet retreats from the chaos, nursing her own injuries, Marlowe uncovers that Carlotta is, in fact, an island off the coast of Peru. Rigby's next meeting with Kitty in a local cafe reveals essential details about the island's inhabitants, which include her new partner, Rice. Carlos, a no-nonsense policeman, warns Rice to exercise caution regarding the island's unsavory characters.
The following day, a local makes Rigby an offer—to leave the island and avoid further trouble. However, Rigby remains resolute in his quest for the truth, even amidst growing dangers. He ventures into Kitty's room, where she discloses that Rice is, in fact, a Nazi agent and confirms her clandestine collaboration with Marlowe to dismantle the enemy's endeavors.
As Rigby probes deeper, he learns that Dr. Forrest, a distinguished scientist, had been kidnapped by the Nazis, leading to a staged death to conceal their operation. Before his death, Forrest unveiled a shocking revelation—a potent cheese mold possessing corrosive qualities that posed a significant threat to America. The FOC was established to counter this looming danger, yet their efforts were thwarted when the Immer Essen, intended to transport a list of Nazi agents, became ensnared within the conflict.
Rigby’s life devolves into turmoil as he finds himself in the clutches of the Nazis, but is saved by Juliet and her father's devoted butler, Field Marshal Wilfried von Kluck. While battling his way to freedom, he uncovers a startling truth—the deadly cheese mold had been deployed to obliterate Terre Haute, Indiana. In a desperate bid to thwart the Nazis, Rigby allies with Juliet and Rodriguez, leading to an exhilarating climax that promises to determine the fate of all parties involved.
