I reach up, bringing my hand to Alex's face. It only takes a moment for me to find the bump on his forehead, and though he doesn't make a sound when my fingers brush against it, I feel him stiffen, so I know he must be experiencing some pain as well.

"Your lump is pretty big," I say, "but I still think mine is bigger."

"On the contrary, I think mine is." His finger traces the edge of my bump. "You definitely have the harder head."

"What are the symptoms ...