凯蒂，罗马的一个摄影师，一次意外的目击了一名手挥利刃，带黑色手套的年轻女杀手。于是凯蒂和她的未婚夫阿尔贝托去警方进行报案，发现先前其他目击犯罪的证人都一一死亡。凯蒂担心她会成为下一个受害者。此时她的一位跳芭蕾舞的朋友玛格达也残酷杀害，情况难以捉摸。警方也感到困惑，无法找到一个切入点。这时阿尔贝托发现了一个线索：所有被害的都是跳舞的女孩。凯蒂进一步调查，发现了凶手的照片并提醒了阿尔贝托。但是凯蒂却被困在一个偏僻的房间里，疯子凶手正步步逼近......

Stefano, the son of a wealthy businessman, meets a beautiful woman named Lidia while accompanying his father to a meeting with a cardinal. He pursues her through the streets of Venice and a romance develops. Upon returning from an overseas business trip, he is informed that Lidia has been killed in an accident. Soon afterwards, he thinks he recognizes her at a building site, but the woman claims to be a reporter who is obviously involved with gangsters. Furthermore, all evidence of Lidia's death has now been obliterated. Stefano continues to investigate the mystery, uncovering family intrigues

Lidia y Stefano se aman, pero él ha de intimar con Giovanna para atender a los intereses de su padre. Lidia desaparece, y Stefano descubre que mantiene relaciones con un capo de la droga. Éste la hiere de gravedad, y Stefano acude en su auxilio.