Norman becomes homesick after receiving a letter from his mother. He goes for a walk by the river and meets Mike Johnson, a lieutenant from the nearby U.S Army base who shows him how to fish. Meanwhile, Mary agrees to help Polly and Dennis find out if Grainger is a spy. On the way back to the Farm, Polly and Dennis encounter a strange woman who bears a striking resemblance to the woman in the poster Cyril Jenkins showed them. When the woman asks for directions to the village, Polly, convinced she's an enemy spy, intentionally sends her the wrong way and thinks they've seen the last of her - until she turns up at the front door!