When opera singer Riley Williams agrees to sub as a musical-theater performer on a luxury Rhine/Moselle River boat cruise, she gets more than she bargained for. Not only does she have to come up with 250 Broadway songs, she must dance with the male passengers. Dance-the subject she nearly failed in her conservatory courses, and the cause of her recent flop in an opera house. To make matters worse, she overhears two terrorists at a café in Antwerp, Belgium, discussing the transfer of deadly Agent X to the highest bioterrorist bidders. Interpol Agent Jacob Coulter, an anti-terrorism desk analyst in Brussels, Belgium, insists on serving as an undercover agent after his best friend Noel is murdered by terrorists from the cell he infiltrated in Brussels. Shortly before Noel dies, he manages to tell Jacob snippets of the terrorists' plans. Plans that seem to involve the same river boat cruise Riley is on. When Interpol learns of Riley's encounter with terrorists at the café, Jacob's supervisor insists he work with her to identify the terrorists and retrieve Agent X. But their relationship is fraught with distrust because of Riley's suspicious past and a romantic attraction neither of them wants.