That's the book!

A couple of weeks ago I was trying to remember a book in which children run away and live in a museum.

Today, someone posted a clip from Clue on Ravelry, which prompted me to look up Madeline Kahn's filmography, and then follow from there to the entry on Wikipedia about the book:
"From the Mixed-Up Files of Mrs. Basil E. Frankweiler".

Must remember to see if the Guelph library has a copy.