Naina Talwar (Deepika Padukone) is a shy and nerdy medical student. She studies constantly and always tops her classes, but she feels like an outcast due to her introverted nature. An encounter with an old classmate, Aditi Mehra (Kalki Koechlin), makes her realize that she wants more from life than high marks. Thus, she makes an impulsive decision to follow Aditi on a hiking trip into the Himalayas, up to Manali without informing anyone. During the hike, she renews her friendship with other former classmates, Kabir "Bunny" Thapar (Ranbir Kapoor) and Avinash "Avi" Arora (Aditya Roy Kapur). Kabir is a handsome charmer whose dream is to wander and discover the world. He does not plan to marry or settle down. He lives with his supporting father whom he loves very much, and his step-mother. During their trip, seeing Aditi's silent reactions to Avi's constant flirting with other girls, Kabir and Naina realize that she is secretly in love with Avi, but do not bring the matter to surface.