Young Errol Winston arrives in London in search of a job and a better life, but he finds himself homeless when the city's racist landlords refuse to rent to him. At last he seems to have a stroke of good luck when he accidentally winds up at the front door of Mr and Mrs Didcot, who offer to let him stay. The elderly couple seem kindly and harmless enough, but Errol will soon discover that behind the veneer of apparent respectability a dreadful...