Kang Hye-soo is a single mother whose husband died in a car accident and she now raise her daughter on her own. She works for Han Ji-hoon, a rich man comes from a chaebol family who is looking for a liver donor for his mother because she contracts a serious liver disease. When Hye-soo learns she has an inoperable brain tumor and Ji-Hoon's problem, she decides to be the donor, in exchange for enough money to provide for her daughter when she passes away. To make it legally happen, the two enter a marriage contract.