Principal's on the Roof

The principal of Kill and Gwen's school promised to spend the morning on the roof if the kids read one thousand books during their reading marathon -- and they did! Now he's on the roof, and he's going to read an original science fiction story Gwen wrote.But he could fall off the roof if he doesn't stop sneezing. Is it a coincidence that Gwen's story is about aliens who live on roofs and make humans sneeze? Fletcher knows that Gwen would never pull a dangerous practical joke just to make her story come true. But can he prove it before Gwen's in big trouble?