Quickly she grabbed a vial and poured it onto one side of the plate, It was absorbed quickly and didn't run over the plate.
The other Marie came back, wrapped in her own towel, and they began to eat--while the first Marie was careful not to eat from the part of the plate she poured the vial in.
Soon the first Marie saw the second eat the piece of potato with the vial soaked into it, and said "Ha, ha, I got you!"
"You got me? Huh?"
"I poured a vial in that food! There needs to be only one of us when Mary comes home! She can't see two!"
"What vial was it?" She was already starting to transform.
"I dunno...."
"I feel funny," said the second Marie. "Oh, look at this!" She whipped her towel off.
"Yo... you're..."
"I'm a boy! Change me back!"
"I guess I have to. If Mary sees you like this she still sees two of us so I can't hide you this way."
Just then came the sound of a key in the door. Mary opened the door, carrying in a bag of clothes... and saw the female and male versions of Marie. They looked identical at that age, but the male version had taken his towel off, and it was very obvious what had happened. "Marie!" she said. "Look at what you did! This means..."