Black Knight is a love story between a woman who is waiting for the love of her life and a man who is willing to do anything to protect his love. The story spans over two hundred years. Moon Soo Ho is a businessman with a pure heart, but he never shows his true colors to anyone except for Jung Hae Ra, a travel agent who has never traveled abroad. Soo Ho and Hae Ra grew up like siblings in Hae Ra's house, but they got separated later. They meet each other after they grow up and love approaches them as if it were fate. Will their love survive despite all the faltering events?