Mary was very straightforward, so she didn't believe that the vials could actually do anything to her. She plucked one out of the box, and drank some of it. She felt absolutely nothing.
Looking at the vial, she saw a picture of a giant panda. She waited for 5 whole minutes, during which nothing happened.
Mary was quite pleased with herself. She happily munched a large salad, and took a shower. She admired her near perfect form in the mirror.
With nothing left to do, she went to bed. But just before she fell asleep, she could have sworn something was outside her window.