At the end of an ordinary work day, advertising executive Roger O. Thornhill (Cary Grant) hurries from a Madison Avenue office building to a business meeting in the Oak Room bar of the Plaza Hotel. Having just asked his secretary to phone his mother, he realizes that she won't be able to reach her, so he will need to send a telegram instead. When a hotel pageboy passes by calling for 'Mr. Kaplan...Mr. George Kaplan...,' Thornhill flags him down to ask about sending a telegram. This draws the attention of two henchmen, Valerian (Adam Williams) and Licht (Robert Ellenstein), who mistake Roger to be Kaplan because from their vantage point he appears to be answering the page. As Roger steps into the corridor to send his wire, the henchmen abduct Roger at gunpoint and force him into a waiting car.

Wordlessly, they drive him out of Manhattan to a country estate displaying the name 'Townsend' at its entrance. The car snakes up a long winding driveway to the front entrance. A maid lets them in the front door, and Roger is locked inside the library of the mansion. Left alone, he finds a newspaper on the desk addressed to 'Mr. Lester Townsend, 169 Baywood, Glen Cove, N.Y.'

Shortly, the library door opens and there enters an urbane gentleman (James Mason), evidently none other than Townsend himself, followed soon after by his personal secretary, Leonard (Martin Landau). The gentleman addresses his captive as 'Kaplan,' and by his questions, Roger can only assume that the real Kaplan must be some sort of secret agent on this man's trail. Roger tries to convince him that his name is Thornhill and has never been anything else, but his captor will not hear of it. To 'prove' his point, the man proceeds to recite the elusive Kaplan's recent itinerary of hotels, cities, and ever-changing home towns, including Kaplan's present occupancy of room 796 at the Plaza Hotel, and his future stops in Chicago and Rapid City, South Dakota. To find out how much 'Kaplan' knows about his organization and their current arrangements, he puts Leonard in charge of extracting the information while he withdraws to join Mrs. Townsend (Josephine Hutchinson) and their party guests. Leonard unseals a fifth of bourbon taken from a liquor cabinet, and with the aid of Valerian and Licht, he begins to force the whiskey down Roger's throat.

Having failed to get any information from their victim, Valerian and Licht place the severely intoxicated Thornhill behind the wheel of a Mercedes on a seaside highway under cover of darkness, planning to guide him off of a cliff to his death. Almost unaware of his surroundings, Roger comes sufficiently alert at the last moment to push Valerian out of the car and start driving for himself. The two thugs follow him down the winding highway in their own car. Roger, on the verge of passing out and plagued with double vision, manages to careen his way down the cliffside highway without hitting anything. As he slams on brakes to barely avoid running over a bicyclist, a pursuing police car plows into the rear of the Mercedes, and a third car plows into the rear of the police car. Finding themselves overmatched, the two henchmen drive away leaving Roger in police custody.

Roger tells everyone at the police station how his captors had tried to kill him, but in his drunken condition no one pays any attention to his bizarre story. One of the policemen mentions that the Mercedes Roger was driving was stolen. Roger phones his mother to let her know he is at the Glen Cove police station for the night. In the morning, Roger and his attorney Larrabee (Edward Platt) face the judge, with Roger's mother, Clara Thornhill (Jessie Royce Landis), looking on in weary bemusement. The judge gives Roger a chance to prove his doubtful story, and continues the case over to the next day.Wkrótce, biblioteka otwiera drzwi i wchodzi jeden urbane Gentleman (James Mason), oczywiście nikt inny niż sam Townsend, a następnie szybko po jego osobisty sekretarz, Leonard (Martin Landau). W gentleman adresy jego niewoli 'Kaplan', a jego pytania, Roger może jedynie przypuszczać, że rzeczywiste Kaplan musi być pewnego rodzaju tajny agent na tego człowieka tras. Roger próbuje przekonać go, że jego nazwisko jest Thornhill i nigdy nie było nic innego, ale jego captor nie będą jej słuchać. Aby 'udowodnić' jego punkt, człowiek przechodzi do recytuja elusive Kaplan niedawno trasę hoteli, miast, i stale zmieniających domu miast, w tym Kaplan obecną obsadę pokoju 796 w hotelu, a jego przyszłość przestaje w Chicago i Rapid City Południowa Dakota. Aby dowiedzieć się, jak wiele 'Kaplan' wie o jego organizacji i ich obecnych ustaleń, sam Leonard za ekstrakcji informacji, podczas gdy on wycofuje się dołączyć do pani Townsend (Josephine Hutchinson) oraz ich strony gości. Leonard unseals jedną piątą Bourbon pobranych z barek, a także z pomocą Waleriana i Licht, zaczyna życie na whisky w dół Roger's throat. Po nie otrzymasz wszelkie informacje z ich ofiary, Waleriana i Licht miejsce na poważnie zatruty Thornhill za kołem o Mercedes morzem na autostradę pod osłoną ciemności, planuje przewodnik go wyłączyć z urwiska do jego śmierci. Prawie nie zdawać sobie sprawy z jego otoczenia, Roger jest wystarczająco wpisu w ostatniej chwili do pchania Walerian z samochodu i rozpoczęcia jazdy dla siebie. Dwa thugs się go do likwidacji autostradą we własnym samochodem. Roger, na skraju przechodzi obecnie plaga i podwójne widzenie, zarządza się jego sposób careen ustanawiające Cliffside autostradą bez bicia czegokolwiek. Jak on slams na hamulce do zaledwie unikać używania przez rowerzystów, realizujących radiowóz plows do tyłu Mercedes, a trzeci samochód plows do tylnej części radiowóz. Znalezienie się overmatched, dwóch popleczników dysku Roger pozostawiając daleko w areszcie policyjnym.