It was Lucia's fault. No one was going to say it was Lucia's fault, but it was.

She dared him. Mother would say he was too old to fall for dares, even though she knew just how to say them so he'd agree. There were those great big walls around the city, and really, who puts walls there if you're not supposed to climb them? And Lucia said she'd got that soft fall spell working. Which she had; when he fell off the wall, it didn't hurt.

It just dropped him right on top of a demon.