During World War II, a small group of survivors is stranded in a lifeboat together after the ship they were traveling on is destroyed by a German U-boat.

In order to help bring Nazis to justice, U.S. government agent T.R. Devlin recruits Alicia Huberman, the American daughter of a convicted German war criminal, as a spy. As they begin to fall for one another, Alicia is instructed to win the affections of Alexander Sebastian, a Nazi hiding out in Brazil. When Sebastian becomes serious about his relationship with Alicia, the stakes get higher, and Devlin must watch her slip further undercover.

London, 1929. Frank Webber, a very busy Scotland Yard detective, seems to be more interested in his work than in Alice White, his girlfriend. Feeling herself ignored, Alice agrees to go out with an elegant and well-mannered artist who invites her to visit his fancy apartment.

London. A mysterious serial killer brutally murders young blond women by stalking them in the night fog. One foggy, sinister night, a young man who claims his name is Jonathan Drew arrives at the guest house run by the Bunting family and rents a room.

一位新房客（艾佛•诺维洛饰）被房东太太（玛丽•奥尔特饰）和她丈夫（阿瑟•切斯尼饰）怀疑有可能是恶名昭著的“连环杀手”，但他们当时装模特的女儿黛西•邦廷（琼•特里普饰）却被他深深吸引。黛西的男友警探乔•贝茨（马尔科姆•基恩饰）产生了嫉妒，于是在房东太太的教唆下获得了搜查令闯入了他的房间。然后警察找到了一把手枪和一张标明以往杀人地点的地图，以及一张第一个受害人的照片。房客辩称那个女孩是她的妹妹，他只是在寻找杀人凶手，可是警察还是逮捕了他。在黛西的帮助下，他逃了出来，但因为戴着手铐在酒吧被人发现，于是，他被逼入了墙角。
本片有一个难忘的镜头被希区柯克称为是在默片时代替声音的拍法，就是镜头里出现“房客戴着手套的右手在楼梯扶手上慢慢下滑。