Claire Bennett, born into poverty, was abandoned by her mother at a young age. In order to take care of her younger sister Lily, who suffered from psychological trauma, she dropped out of school at fifteen and started working, betting almost her entire life on her sister. To pay for the expensive treatment, Claire takes part in a special recruitment offer from Boston's top wealthy family, the Smith family—a monthly salary of one hundred thousand dollars to serve as a nighttime companion for the fourth young master, Alexander Smith, who has long suffered from insomnia. Facing nearly harsh layers of assessment, she stands out with her calmness, observational skills, and unconventional way of solving problems, and after accidentally saving the Smith family's old madam, she formally steps into this seemingly glamorous family that hides secrets within. The cold and arrogant Alexander never believes in this girl who suddenly intrudes into his life, but Claire's first real test is to comfort the wealthy heiress Vivian, who has completely collapsed after being betrayed by her fiancé. Everyone thinks Vivian has gone mad, but Claire sees the pain behind her anger, and accompanies her to expose the love scam between Ethan and Camille, helping her regain the dignity, career, and self that were buried by love.