In Sex/Life, Owen cheated on Christina with Billie, his free-spirited and adventurous ex-lover. Their affair occurs while Owen is married to Christina, creating the central tension in the series as Christina discovers his betrayal and grapples with her feelings of hurt, jealousy, and desire. Billie represents the passionate, impulsive side of Owen’s past that contrasts sharply with the stability and family life he has with Christina, which intensifies the emotional stakes for all the characters involved.
The cheating is pivotal to the story because it forces Christina to confront her own dissatisfaction, the complexity of love and desire, and the challenges of maintaining a marriage in the face of temptation and unresolved past connections. Owen’s infidelity acts as a catalyst for much of the drama, shaping the characters’ decisions and the series’ exploration of intimacy, trust, and personal fulfillment.