Time Out says
Nestled away in their vacation house, Mirjam (The Lives of Others’ Gedeck) and André (Devor) are ready to put in some time sailing on the bay and whiling away their days. With their teenage son and his very young girlfriend (Lohde) along for the trip, the scene is set for an idyllic family getaway. Then the boy comes home alone one afternoon; it seems his sweetheart decided to impetuously hang out with an older American guy (Seeliger). Though nothing taboo happens, Mom immediately senses that both the coquette and this stranger get off on flirting with each other. She initially feels protective of the girl. Then, once Mirjam starts sleeping with the interloper, she begins viewing the Lolita as competition. These situations never end well.
Stefan Krohmer’s bourgeoisie-breakdown drama wrings its central love triangle for every ounce of domestic dread it’s worth, throwing in some narrative shockers that suggest someone has studied all of Polanski’s movies. Then comes the denouement, which will only cause you to shake your head in disbelief. Gedeck’s performance, however, is a humdinger: Alternating between polite probing and adolescent fidgeting once lust takes over, her turn props up this intellectual potboiler even when it stumbles and falls.