What Every Woman Knows centers around the emotional development of John Shand, a humorless young Scotsman whose meteoric political success is due entirely to his wife. However, John fails to recognize the influence and intelligence of his plain wife. While a poor student, he took to regularly breaking into the home of the Wylie family in order to access their library and further his studies. He is soon caught by Alick Wylie, the head of the family, and his two sons, David and James. John makes an agreement with the Wylie men that they will financially support the rest of his studies until he has begun to make his way in the world. However, in return for this support, he must marry Maggie, Alick’s plain, unassuming daughter after 5 years. Despite being offered a get-out clause by Maggie, John sticks to his promise, and Maggie works tirelessly behind the scenes to make her husband a political success. When his success goes to his head and he declares his love for socialite, Lady Sybil, it takes the threat of permanently losing Maggie and her political input to make him realize the valuable loyalty and ability of the woman by his side.