New York private eye Shamus McCoy likes girls, drink and gambling, but by the look of his flat business can't be too hot. So an offer of $10,000 to finds some diamonds stolen in a daring raid with a flame-thrower is too good to miss. His investigations soon get pretty complicated and rather too dangerous. At least along the way he does get to meet Alexis.

Inquisitive journalist Grace Collier is horrified when she witnesses her neighbor, fashion model Danielle Breton, violently murder a man. Panicking, she calls the police. But when the detective arrives at the scene and finds nothing amiss, Grace is forced to take matters into her own hands. Her first move is to recruit private investigator Joseph Larch, who helps her to uncover a secret about Danielle's past that has them both seeing double.

The story concerns the difficulties and reactions of Maddalena (Sophia Loren), an Italian visitor to New York City. She has come to the country carrying a huge mortadella sausage which she intends as a gift for her fiancé. But Customs do not allow processed meat to enter the U.S., so she is held at JFK airport...