One Night, Twin Flame

Sarah comes back to the country to get treatment for her son, who has leukemia. The treatment she has in mind is to find the boy's father and have another child with him. The boy is five. Sarah was the young lady of the Soo family when she became pregnant by a man she had spent one night with and did not know, and the family put her out for being pregnant and unmarried. Her half-sister Lily looked into the man and found he was Ethan, the heir of the Chou Group. Sarah gave birth to twins. Lily took the elder one, who was healthy, and left the younger, who was sick, with Sarah, and then married into the Chou family and got position and power there. Sarah's son is that younger twin. Sarah and Ethan run into each other again, and the two boys decide to help their parents get together.