Ethan (Mark Duplass) and Sophie (Elisabeth Moss) have been married for many years, and their feelings have faded and finally reached a deadlock. In order to save their marriage, the two decided to consult a love expert. Under the advice of the love expert, Ethan and Sophie came to a mysterious place for vacation. The love expert told them that the couples who had come here for vacation eventually had a happy marriage. At the resort, Ethan and Sophie met another couple, and what shocked them was that the couple looked exactly like them. Driven by curiosity, Ethan and Sophie decided to stay. As time went by, Sophie gradually fell in love with another Ethan. At the same time, Ethan began to be confused whether his wife was the one who had slept with him for many years.