River sprinted across the lawn towards the where she knew the Ravenclaw would be. She ran up to the boy and skidded to a halt, "Sherlock, sweetie," she said between gasps for breath, "You don't know who I am, but it's really important you listen to me, alright?" She reached into the bag hanging from her side and pulled out a glass vial, that she pushed into his hands. "Someone is going to get hurt, very badly. When they do, you need to give them this."
Sherlock frowned at the girl, not really understanding what was going on. 'Who are you?' he thought. 'How do you know who I am? How do you know what's going to happen? Why are you telling me?' But instead of asking, he decided it was best if he just did as she told him, and hesitantly accepted the vial.
