Helena was taken by her fellow colleagues while going to work and they abducted her. Kai, who said to be her best friend was involved. One night, they decided to pull a prank at her but it ended to be real. They killed her! But one morning, Helena came back to work like nothing happened and she didn't remembered anything at all. She treated them as a normal person but soon they realized that she's not only an ordinary girl, she had secrets and that's what she called their "Tradition".