Third big-screen adaptation of John Buchan's classic novel. Mining engineer Richard Hannay (Robert Powell) is on a brief visit to England when his neighbour Colonel Scudder (John Mills) warns him that foreign 'sleeper' agents are at work, planning to pre-empt global war by murdering a foreign dignitary. When Scudder is murdered by the agents Hannay finds himself under suspicion by the police, and goes on the run in a bid to both prove his own innocence and expose the enemy spies.