Jane Summers joins Sinclair Industries with a fresh master's degree and a stubborn belief that big corporations can go green. She does not expect to catch the attention of the CEO. Alexandra Sinclair runs her company the way she runs her life. With cold precision and walls built from a lifetime of proving herself to a father who wanted a son. The Ice Queen, they whisper. When Alexandra discovers that her father's will requires her to be married with a child by forty or lose everything, she makes a calculated choice. Jane is the only employee who isn't loyal to her scheming cousin. The only one she can stand. The only one who ever brought her a plant. Jane agrees to one year. A marriage in name only. A sustainability division with real power in exchange. What starts as a contract turns into something neither of them expected. Late nights in the library. Towers built with a three-year-old girl who has been in three foster homes and doesn't trust anyone to stay. The slow, aching realization that the walls are coming down. But Alexandra's cousin discovers the contract. The adoption is threatened. And Jane has to decide if one year is enough or if she wants forever. The Sinclair Heir is a sapphic marriage of convenience romance about contracts that become something more and the woman who keeps her promises.