Twenty-nine-year-old top engineer Claire signs a contract marriage with Damian, the president of the Cross Group: an annual salary of $1.5 million, and taking over his chaotic wealthy family. Waiting for her are three kids, each with their own quirks — the deep and sensitive eldest son Leo, the rebellious and precocious daughter Sophia, and the mischievous little son Milo, with constant water fights, pranks, and tricks. Claire uses her engineer's logic to handle every challenge, setting rules while giving warmth, and outsmarting high school nemesis Bianca's provocations, as well as the kids' mother Selena's behind-the-scenes scheming. As this genius stepmom gets the wealthy family back on track, the contract couple also begins to develop genuine feelings while fighting side by side.
