One morning just like any other in Madrid, two perfect strangers, Sara and Jaime, are just two more people standing on an underground platform. A man falls onto the tracks as the train pulls up. For everyone there, it´s a tragic accident. But not for Sara. Horrified, she believes she saw Jaime push the victim onto the tracks. She decides to blackmail the killer. The hunter and her prey become involved in a perverse and increasingly intimate relationship, at a distance.