On a rain-soaked night, Matthijs van de Sande Bakhuyzen voices the story of his last summer, a time when a rural life in Overgier gives way to the sprawling rhythm of Amsterdam. While finding his way to a new home, he crosses paths with Sallie Harmsen as Sanne, who pulls him into an exclusive party hosted by Géza Weisz playing Mario and a fearless womanizer named Marlon, brought to life by Manuel Broekman. Despite a rocky first impression, Dennis receives a coveted invitation key, owed in part to Marlon’s pressing need to raise 3,000 euros owed to Yahya Gaier in the form of Achie.
Sanne, unaware that her fling with Marlon is only a one-night stand, pushes to promote the party across the city. She drags along her closest friends, Iris, a sharp-witted woman played by Isis Cabolet, and Lotte, a DJ portrayed by Gwen Pol. The trio tries to forget their own dramas as Iris recovers from a painful split, and Lotte wrestles with a decision about dating after a moment of indiscretion. To escape the tension, the women seek out a hotel adventure, while Dennis finds himself being hazed by Mario and Marlon. In a wild turn of events during a drug-soaked moment, the group imagines having their own penguin, and Dennis, eager to fit in, goes along as they steal one from the Artis zoo.
The morning after, Dennis wakes with a heavy hangover and sets out to return the penguin to Artis, only to fail in his mission. Sanne learns the truth from Mario and Marlon and is handed three keys for the exclusive party, on the condition that Dennis stay silent about what happened and get the penguin back to the zoo as soon as possible. Yet Marlon tricks Dennis into bringing the penguin to the party, hoping Sanne won’t mind its arrival.
That night, chaos explodes at the event. Peter is humiliated by Iris after his infidelity is broadcast on a screening, while Mario spirals into cocaine-fueled disappointment as he faces rejection from several women. Achie arrives, still nursing his earlier injury from Mario, demanding repayment. The tension peaks as law enforcement closes in, arresting the penguin thief. Marlon tries to slip away with Sanne, only to be dumped when she chooses to stand by Dennis. Marlon is beaten by Achie and his associates, and Dennis spends a night in a cell, only to be released the next morning for lack of evidence.
In a final twist, the narration reveals itself: the entire tale is Dennis’s own recounting. The closing revelation shows Sanne severing ties with Marlon and starting a new relationship with Dennis, closing the summer’s story with a quiet, unexpected turn of affection.
