A group of friends get together during the last weekend of August 1939 at the rural retreat named Longwood, a few miles from Portsmouth. Their host, American novelist and socialite Georgina Riley, is scheduled to leave for her native New York to marry her childhood sweetheart. With a possible war looming, they decide to have an 'end of the world' party. The following morning Georgina is discovered in her bedroom covered in blood, her throat slit, barely alive. Her maid is dead. Detective Inspector Rudman arrives to investigate. But with Germany's invasion of Poland a week later the suspects disperse across the land, some to the armed forces, others to reserved civilian jobs. Rudman does not give up. Wherever they are he can be found. Whatever the defeats and victories of the Allied cause, he has only one aim: to find the person responsible for what happened that weekend at Longwood. The war ends; some have survived, some not. And then comes an invitation to spend another weekend at Longwood. The message is that Rudman has found the evidence he has been looking for. One of the surviving couples motor slowly down to Portsmouth, remembering the original weekend, the trials and the tribulations of the past years, and wonder: what will be revealed during the coming weekend at Longwood?