The Double Clue (S03E07)

For the first time in his life the genius Belgian detective, normally impervious to womanly wiles, falls in love. The object of his unaccustomed affection is a beautiful Russian, the Countess Vera Rossakoff, whom Poirot meets during his investigation into four high society jewel robberies. While Poirot's attention is captivated by the Countess, Hastings and Miss Lemon pursue their own misguided inquiries into the crimes. (iTunes)