In the novel Dead Man's Folly, Marlene Tucker was a Girl Guide. During the Murder Hunt, created by Ariadne Oliver for the fête, Marlene was supposed to act as the murder victim in the boathouse.
Marlene was described as being "a well-developed girl of fourteen", and she had a "plain, rather spotty face". Mrs Oliver told Poirot that Marlene was rather dumb, and that she sniffed.
During the preparations for the fête, Marlene met Poirot, and told him that she was to be the corpse for the Murder Hunt. She was disappointed that she would not have any blood on her, and said that she would have liked to have been stabbed, and have lashings of red paint. She was of the opinion that in a murder, one ought to have blood.
Marlene asked Poirot if he had seen "lots of murders", and if there had been any sex maniacs among his cases. She told him that she liked reading about sex maniacs, and that she believed they had one in the area, because her grandfather had seen a woman's body in the woods once. However, she also said that her grandfather was "batty", and so no one listened to what he said.
Marlene was found dead in the boathouse, sprawled on the floor by the window. This was the exact position she was supposed to be in when she was acting as the corpse for the Murder Hunt. She had been strangled with a clothes line.
Miss Brewis had taken a tray of sweet cakes and a raspberry fruit drink to Marlene at about a quarter past four. At that time, Marlene had been alive and well, and had let Miss Brewis into the boathouse. According to Miss Brewis, Marlene was also eager to know how people were progressing in the Murder Hunt.
According to Marlene's mother, Mrs Tucker, Marlene would have occasional quarrels with her teacher or her peers, but it was never anything serious, and there was no one who had a grudge against her.
Mrs Tucker also said Marlene "talked silly often", but had never mentioned anyone who might have been an enemy. Marlene talked about make-up and hair-dos, and when she had money she would buy perfume and lipstick, and hide them. Mrs Tucker also mentioned that Marlene had received a lipstick and scarf from Sally Legge.
Marlene had a pile of comics with which to amuse herself in the boathouse, and had doodled some words there, such as, "Jackie Blake goes with Susan Brown", and "Peter pinches girls at the pictures". Poirot suspected that boys had not paid any attention to Marlene, and that she had been frustrated about it. So instead, she had gotten a vicarious thrill by "spying and peering at" other people.
Marlene's sister, Marilyn, later told Poirot that Marlene did indeed "snoop about a bit". She would see "goings-on", would promise not to tell, and would be given money to keep quiet. The lipstick and scarf, which her mother believed to be gifts from Sally Legge, were actually bought using this money, along with some perfume and foundation cream. Marlene had hidden these items at the back of her drawer, under her winter vests. She used to go into the convenience at the bus stop and make herself up, when she went to the cinema.
Poirot surmised that Old Merdell had told Marlene about seeing a woman's body in the woods, and had mentioned that Sir George Stubbs was really James Folliat. He imagined that Marlene had hinted to Sir George that she knew these things, and had been paid some money to keep quiet.