國防大機密
原始标题: The 39 Steps
音樂廳中傳來槍聲，觀眾們一片驚慌。一位外國女子（Lucie Mannheim 飾）詢問理查德‧漢內（Robert Donat 飾）是否可以在他家中過夜。次日該女子在被殺之前告訴理查德必須阻止間諜組織「三十九級台階」將國家機密偷偷送出英國。漢內為了證明自己並不是殺人兇手無奈前往蘇格蘭高地尋找線索，在火車上他尋求一位叫做帕梅拉（Madeleine Carroll 飾）的金髮年輕女子幫助，但她卻馬上向警察告發了他。他找到了「三十九級台階」的領導人喬丹教授，但隨即被陷害入獄。僥倖逃脱後又由於帕梅拉的告發被兩位偽裝成便衣警察的人帶走，並且他們還把帕梅拉和他銬在了一起。於是兩人攜手逃脱了出來並取得了互相的信任，然後他們再次回到音樂廳，漢內看到了上次就見過的表演。他向號稱可以回答任何問題的「記憶先生」（Wylie Watson ）提問：「什麼是三十九級台階「，於是……
演员
| 演员 | 角色 |
|---|---|
| Robert Donat | Richard Hannay |
| Madeleine Carroll | Pamela |
| Lucie Mannheim | Annabella Smith |
| Godfrey Tearle | Professor Jordan |
| Peggy Ashcroft | The Crofter's Wife Margaret |
| John Laurie | John the Crofter |
| Helen Haye | Louisa Jordan |
| Frank Cellier | Sheriff Watson |
| Wylie Watson | Mr. Memory |
| Gus McNaughton | Salesman on the Flying Scotsman |
| Jerry Verno | Salesman on the Flying Scotsman |
| Peggy Simpson | The Jordans' Maid |
| Matthew Boulton | Fake Police Officer (uncredited) |
| Pat Hagate | M.C. Who Introduces Mr. Memory (uncredited) |
| Alfred Hitchcock | Man Walking Past Bus (uncredited) |
| Carleton Hobbs | Fake Police Officer (uncredited) |
| Elizabeth Inglis | Professor Jordan's Daughter Pat (uncredited) |
| Quinton McPherson | Clergyman on the Flying Scotsman (uncredited) |
| Frederick Piper | The Milkman (uncredited) |
| Hilda Trevelyan | The Innkeeper's Wife (uncredited) |
| Ivor Barnard | Political Meeting Chairman (uncredited) |
| Ex-Det. Sergt. Bishop | Police Sergeant (uncredited) |
| Wallace Bosco | Palladium Doorman (uncredited) |
| Vida Hope | Usherette (uncredited) |
| James Knight | Detective at London Palladium (uncredited) |
| Miles Malleson | Palladium Manager (uncredited) |
| John Rae | Audience Member at Political Meeting (uncredited) |
| John Turnbull | Scottish Police Inspector (uncredited) |
| S. J. Warmington | Scotland Yard Man (uncredited) |
| Charles Bennett | Second Passerby Near the Bus (uncredited) |
制作人员
| Role | Name |
|---|---|
| Director | Alfred Hitchcock |
| Producer | Michael Balcon |