"Slughorn allowed us to each take a vial of our potion, in case we ever found someone we might want to test it on, you know a girlfriend or something perhaps." He thought about Draco and Hermione and wondered whether or not it was his place to tell Narcissa when Draco himself didn't even know, eventually he decided against it and pushed on. "Last night I had my potion sitting on a table and one of the girls that is becoming an animagus with us spilled it. She could smell it, she could smell  me."