A Will Hay double bill. In 'Oh, Mr Porter!' bungling station master William Porter (Hay) is appointed to the run down station of Buggleskelly in Ireland by the resentful Superintendent. When he charters an early morning train for a sinister one-eyed man, his staff, Harbottle (Moore Marriott) and Albert (Graham Moffatt) are suspicious. They investigate, and discover that arms smugglers are using a deserted railway tunnel as a base. Whilst in 'Convict 99' disgraced teacher Benjamin Twist (Hay) finds himself put in charge of a prison for hardened criminals when he is mistaken for a tough prison governor. When he celebrates by getting drunk, Twist ends up behinds bars himself.