American pharmaceutical executive Walter Richmond takes a business trip to Amsterdam, accompanied by his wife Cathryn and their 10-year-old daughter Melissa, who has been mute ever since an accident some time ago. To communicate, Melissa uses a small magic marker board that she wears around her neck. Melissa makes a trip to the ladies' room at the hotel De L'Europe and gets separated from her parents. Melissa wanders out of the hotel and onto the street, where she witnesses the murder of Simon Van Der Molen, the attorney representing Walter's Dutch client. Unfortunately, Melissa is spotted by the killers, who are hit man Bruno Decker and his employer Rudolph Hartman, who turns out to be Walter's client. Hartman had Van Der Molen killed to prevent Van Der Molen from revealing the side effects of Hartman's new medication, which he's marketing to Walter's firm.