US Congressman Arthur Prouty insists that Jessica attends a Washington trade reception where he can hand her a copy of his own fly-fishing book. Actually a short encrypted note is slipped into it by Soviet embassy trade representative Yuri Lermentov. At night he slips into her hotel suite to retrieve it, but is killed by someone escaping. Jessica and police Lt. Blaisdell get little out of her British intelligence friend Michael Hagarty, who was in rough negotiations for a crucial list with Lermontov. He's arrested, leaving Jessica to find and trap the killer.