As the tumultuous year of 1914 unfolded amid the chaos of World War I, Allied forces gathered at the Yser Bridge in Belgium, strategizing their next move. Among them, Captain Rens (portrayed by Jon Finch), demonstrated caution and decided to wait before launching an attack. However, the brilliant Hercule Poirot, brought to life by Kenneth Branagh, proposed a bold approach: to strike within seven minutes, cloaked by a gas cloud that would momentarily blind the enemy. The soldiers, inspired by Poirot's audacity, succeeded in their assault against the Central Powers. Just as Rens commended Poirot for his ingenuity, tragedy struck when he accidentally triggered a bomb that destroyed the bridge, resulting in Rens' death, several injuries among the troops, and leaving Poirot gravely wounded.
While recuperating in a hospital, attended by his devoted nurse and lover Katherine (played by Susannah Fielding), Poirot revealed the shocking extent of his disfigurement. Katherine, showing unwavering support, offered comfort, suggesting that a neatly trimmed mustache might help mask his scars, an intimate moment that solidified their bond.
Fast forward to 1937, Poirot finds himself amid the vibrant atmosphere of a London nightclub, enchanted by Salome Otterbourne (played by Sophie Okonedo) and her sultry voice captivating the audience. Her niece Rosalie (portrayed by Letitia Wright) cleverly navigates the aristocratic patrons to collect their payments. The dance floor comes alive as the passionate couple Simon Doyle (partnered by Armie Hammer) and Jacqueline "Jackie" de Bellefort (portrayed by Emma Mackey) lose themselves in a tango, their chemistry igniting the space as Salome's melodies fill the air. However, Jackie’s unease heightens as her lover’s attention drifts toward the stunning Linnet Ridgeway (played by Gal Gadot), who proposes a job opportunity for Simon just before their wedding.
Six weeks later, Poirot is in Egypt, leisurely sipping tea near the majestic Sphinx when his peace is interrupted by a man flying a kite atop the pyramid. To his surprise, it’s his old friend Bouc (played by Tom Bateman), who introduces Poirot to his artistic mother, Euphemia (portrayed by Annette Bening). Their focus on the artistic beauty of the pyramid leaves little room for idle chatter.
As Bouc guides Poirot to the luxurious First Cataract Hotel, they discover a cheerful celebration in honor of the newlyweds, Simon and Linnet. The guest list boasts a colorful array of characters, including Euphemia, Salome, and her niece Rosalie; Louise Bourget (portrayed by Rose Leslie), Linnet's dedicated maid; Marie Van Schulyer (played by Jennifer Saunders) and her devoted nurse Mrs. Bowers (portrayed by Dawn French); Andrew Katchadourian (played by Ali Fazal), who handles Linnet’s will; and Dr. Linus Windlesham (played by Russell Brand), her former lover. As they engage in conversation, Bouc hints at potential motives among attendees, including Marie’s disdain for Linnet's wealth and suspicions surrounding Andrew's intentions.
The celebratory atmosphere shifts dramatically with Jackie’s arrival, reigniting the tension stemming from Simon's defection. When Simon and Linnet seek Poirot's assistance in dealing with Jackie’s relentless pursuit, the detective learns of Jackie’s emotional scars and her fixation on Simon that remains even after his engagement to Linnet. The discovery that she harbors a .22 caliber gun amplifies the sense of danger lurking beneath the surface.
After advising the newlyweds to leave the scene, Poirot’s counsel is brushed aside by Simon, who chooses to host the guests on his opulent yacht, the SS Karnak, for continued festivities. Linnet confides her mistrust in Poirot, while external conflicts surface, revealing Andrew’s efforts to acquire significant assets from Linnet, leading to discontent from Mrs. Bowers and others.
As the evening progresses, buoyed by revelry, Poirot and Bouc navigate conversations filled with personal revelations. Bouc's declaration of love for Rosalie intertwines with Poirot's interactions with Salome, who suggests a silent connection between them. However, their evening is darkened when a freak accident nearly claims Simon and Linnet as a boulder tumbles toward them, hinting at more sinister developments.
Upon dining, plans for an early departure are interrupted as the atmosphere escalates with Jackie’s unpredictable behavior. A confrontation erupts when Jackie, caught in a whirlwind of emotions, draws her weapon and injures Simon during a heated argument, triggering the night’s cascade of tragedies.
The next morning brings a wake-up call for the guests as horror strikes: Linnet is discovered murdered, leaving all present rattled. Jackie’s position as the prime suspect fractures as she insists she was bed-bound overnight, igniting the investigation led by Poirot, with the assistance of Simon and Bouc. Delving into their friend's past connections reveals vicious interactions, love triangles, and bitter motives.
The depths of deceit unfold as Poirot interrogates various guests, piecing together fragmented stories of jealousy, heartbreak, and betrayal. Unraveling the intricate web connecting Linnet and her associates, Poirot begins to see a clearer image of the dynamics at play, with revelations regarding Louise’s resentment and Windlesham’s past infatuation surfacing.
Amidst the mounting chaos, Poirot retrieves Jackie's gun, farther complicating the mystery. The stakes rise dramatically as Euphemia produces Linnet's iconic necklace, leading to accusations that expose hidden agendas and spark violent confrontations.
As the tension reaches its peak, tragedy strikes with the murder of Louise, whose lifeless body poses yet another enigma for Poirot to unravel. As evidence continues to surface, the walls begin to close in on those involved. The dramatic revelations draw upon Poirot's sharp instincts, leading to a shocking confession that implicates Simon, and Jackie’s meticulously crafted scheme to inherit Linnet’s fortune reveals a tragic twist of fate.
In a frenzied conclusion, blasted by emotions and betrayal, Simon and Jackie find themselves cornered, their fates intertwined in a tragic end that echoes the destruction they wrought. The guests disperse with heavy hearts as Poirot reflects on love's devastating cost, asserting both his wisdom and scars amid the chaos.
Ultimately, the festive nightclub scene returns us full circle; Poirot emerges altered, symbolizing the deeper wounds of time as Salome takes the stage once more, captivating all with her mesmerizing artistry, while Poirot contemplates the shadows of love and loss, beckoning the scars and secrets he's learned to live with.
