Fi is a story about Can Manay, a celebrated psychologist known for his expertise in the field. Despite being a consummate bachelor who beds women without falling in love, everything changes when he meets Duru. Can becomes immediately besotted with her and even buys the house next door to hers to get closer to her.
Before Can's arrival, Duru lived happily with her musician boyfriend, Deniz. However, Can's mind games start to make her question their relationship, without her realizing the full extent of Can's scheming. As the story unfolds, a cast of characters including Bilge, a student of Can's; Özge, a journalist working on an exposé of the celebrity psychologist; and Deniz himself, will have their lives changed forever by Can's crazed pursuit of love.