On The Rocks Laura and Dean are a couple who have been married for a while from Manhattan, have two daughters, Maya (and Theo) respectively. Laura is a writer, and is stuck in a rut, as she tries to finish her novel. Dean is a young and attractive entrepreneur, is working in a start-up company that deals with technology. He often leaves Laura to take care of their daughters. After returning from a business trip, Dean climbs into bed to kiss Laura. When he realizes her voice, he abruptly ends the kiss and goes to sleep which Laura is a bit confused. The next morning, Laura finds a woman’s toiletry bag hidden in Dean’s luggage and he later informs her that it is the property of his business associate Fiona and offered to transport it into his luggage because she couldn’t fit it in her carry-on bag. On The Rocks HD
Laura decides to confide her doubts regarding Dean to her father Felix who is a wealthy, semi-retired art dealer. Felix is a long-time player, is fond of flirting with every woman who he meets. He believes that men are naturally able to cheat. Convinced that Dean is having an affair Felix suggests an investigation of Dean and urges Laura to look over his phone for incriminating messages on text. Laura reluctantly agrees to do so but finds nothing unusual.
While on a business trip, Dean FaceTimes Laura on her birthday. Dean presents her with a present, the Thermomix which she does not seem particularly enthusiastic about. Laura accepts Felix’s invitation for her birthday dinner despite earlier saying she didn’t want to. Felix reveals that Dean was there with his and was shopping at Cartier for jewellery. As Laura becomes suspicious, Felix picks her up in his classic sports car and convinces her to take a stakeout Dean when he goes to a work dinner. Felix and Dean leave in a taxi with Fiona. Felix speeds through the streets, following them. However, Laura is stopped by two police officers for reckless driving. Felix is the father of one officer, using this to bribe his way out of a ticket.
Felix later discovers that Dean plans to take a trip to an Mexican resort, which Laura isn’t convinced of. Dean informs Laura of the trip on the following day. Upon learning that Fiona is also planning the same trip the suspicious Laura contacts Felix, who convinces her to accompany Dean to Mexico in the hopes of spying on Dean. Felix and Laura finally find Dean’s room in the resort. Laura rushes to confront Dean and is shocked to find Fiona with another woman in her room. In the meantime, Dean calls Laura to inform her that he has left early and is on his way back to his home. Confronted with her error, Laura lashes out at Felix, accusing him of being selfish and berating him for his poor treatment of her mother, on whom he cheated many years ago.
Back in New York, Laura and Dean engage in a passionate conversation, in which they share their respective anxieties and fears She was being a bit aloof from Dean due to his constant business trips, while he said he had been busy working to be a better provider to his family. They come to an agreement and Laura is able to overcome her writer’s block. A few days later, Felix visits Laura and they reconcile. In a restaurant, Dean surprises Laura with the second birthday present of an engraved Cartier watch. Laura removes the Felix vintage watch she received and places it on Dean’s.