Martina Lawrence meets explorer Alan McKenzie while mountain climbing at an Alpine resort. Alan is enchanted by Martina and later, when he meets her twin sister Sylvina at the village post office, he mistakes Sylvina for Martina and she invites him to the hotel for lunch to meet her father and aunt. At lunch, Alan discovers that the girls are twins and, after falling in love with the flirtatious and superficial Sylvina, he proposes to her. Martina, the generous and honest sister, is also in love with Alan, but she nobly sacrifices her love for her sister's happiness. While Alan is away on a mountain climbing expedition, Martina visits her sister and the girls go sailing. When a storm suddenly comes up, Sylvina is drowned and Martina decides to take her place. She soon discovers that her sister has been unfaithful, and when Alan returns home he recounts his wife's infidelities and asks for a divorce. Sensing that she has changed and is unlike the girl he married, Alan is puzzled until Martina discloses her true identity to him, and they lived happily ever after.