Every Thursday, Anna (Sophia Loren) takes a train trip to Winchester to do social work and take a break from her husband and two children. One day, a tiny piece of grit in Anna’s eye provokes an unexpected meeting with Dr. Alec Harvey (Richard Burton), and this chance meeting inexorably becomes a secret affair as their casual friendship turns into a tormenting relationship. Realising the danger to her marriage, Anna avoids Alec, who is unhappy in his own marriage; he pursues Anna with increasing intensity, however. Finding herself weakening, she abandons her social work to steal more time with her new love, and agrees to meet him at a friend’s empty apartment...