The good people of San Francisco, California can sleep a little more soundly.

Last Friday, their city was been made safer by a very special superhero.

Batman and a special Batkid spent the day patrolling the streets and battling crime.

Batkid’s real identity (ssssh, don’t tell anyone!) is five-year-old Miles.

Miles has been winning his own battle, ever since he was just one year old—against a disease called leukemia, which is a form of cancer.

Miles’s leukemia is in “remission,” which means that he is doing very well now. In fact, he started kindergarten this year.