Redemption: the Third Party

This novel tells the story of a sister who uses the time dial to go back in time to save her sister Yang Jingting who died in an accident. But he failed to live past the age of 30. Knowing that she could not save her sister, the younger sister used the time dial to save a high school boy who also died in an accident. Yang Jingting fell in love with him when she grew up. He originally wanted to marry her, but she refused. He was heartbroken when he learned the truth. Yang Jingting finally died of homicide. What happened? Third party: You want to save others, but you can't do anything. You can only watch others fall into danger. In real life, whose third party will you be?