In the beautiful yet isolated villa on the Italian island of Pantelleria, renowned rock singer Marianne Lane finds herself on a retreat with her filmmaker boyfriend Paul De Smedt. This getaway is meant to aid her recovery from surgery; however, she has lost her voice, resorting to gestures and soft whispers to communicate. Meanwhile, Paul is grappling with his own demons, having faced alcohol addiction and a recent suicide attempt. The couple, both newcomers to the island, struggle with the language barrier, complicating their attempts to bond.
Their tranquil holiday is unexpectedly disrupted by the arrival of uninvited guests. Among them is Harry Hawkes, an outgoing music producer and former lover of Marianne, who eagerly embraces the luxury of the villa as though it belongs to him. Accompanied by his daughter, Penelope "Pen" Lanier, who claims to be 22, Harry makes himself at home, inviting friends over and dragging everyone to various attractions and events around the island. His boisterous personality becomes tiresome for Pen and irksome for Paul. However, Marianne finds herself rekindling feelings for Harry. Yet, when their intimacy escalates, she firmly halts it, confessing that while she has love for him, she is committed to Paul.
Pen, with her captivating charm, soon begins to flirt with the troubled Paul, leading to an implicit understanding that he may yield to her advances. Following a night of drinking alone, Harry returns to provoke Paul at the pool, resulting in a fierce confrontation that spirals out of control. In a moment of desperation, Paul submerges Harry underwater, inducing fatal consequences. Realizing the gravity of his actions, Paul attempts to save him but is left helpless as Harry's body sinks to the bottom.
The next morning brings a chilling revelation when their maid discovers Harry's corpse. The police arrive, distracted by a pressing emergency involving refugees washing ashore. Marianne cleverly manipulates the situation by claiming she was asleep and suggesting to the officers that the death was the result of an intruder. Paul, feeling the weight of his secret, lies about his whereabouts to avoid suspicion. However, Pen eventually reveals her fluency in Italian, having pretended otherwise, and shocks them with her true age of just 17.
Haunted by guilt, Paul confides in Marianne that he was responsible for Harry's death but had tried to save him. Before leaving the island, Pen makes a cryptic comment that references something Marianne once told Harry, leading Marianne to react in anger and deliver a slap to Pen's face. Pen, maintaining her composure, boards her flight in tears, unnoticed by Marianne and Paul as they leave in their car. However, their journey is interrupted by the police, where they encounter an officer who, rather than pursuing the case, reveals himself to be a fan of Marianne and requests an autograph. Marianne happily complies, and as they depart, she and Paul share a moment of relief, driving away from the haunting events that unfolded.
