Elementary school book, can't remember the title

[Kaity]

I got this question recently and wanted to get some help finding this book: "I read this book back in elementary school that I haven't been able to find and reread since. I was curious if it was still on the mandatory reading list. It was about a boy who ran away from home and ended up at this random like pocket dimension house on some random street but it was full of other kids that ended up being other run aways but I want to say it was run by witches or something along those lines. Everything was cool if you did what you were told and didn't ask questions but if you got smart to the weirdness, bad stuff would happen. All I remember is that there was some monster dude named Harpo or something along those lines and the main character could only see everything for what it was when he stopped eating the food they provided to all of the runaways. Also at the end the kid goes back to his family more grateful and all of the kids at the house start to disappear."

[SamSpayedPI]

Well, let's start with The Thief of Always. It's not an exact match, but it is one of the most requested books here.

[Kris]

Please note: you must add genre (e.g., children's fantasy or horror?) and plot details to the header/ topic title. Just copy from what you've already written in the first comment. Requests with vague headers are closed because this group is so large. If you need help with this, just post a new comment.