children's adventure book, title lost to my memory

[Jonathan]

I'm trying to find a book from my childhood, but don't remember the author or title. It was published prior to 1988. Based on my memory, the cover of the edition I read was simple - a fox being illuminated by an outdoor light. The story involved a group of kids (3 or 4) that find a treasure map behind a loose brick in one kid's house, which leads them on a li'l adventure in the woods behind the house. In the end, they discover that the parents had been the ones to make the map when they were kids themselves. I "think" one of the kids had a nickname of TumTum or Tum-Tum.

I know this is rather vague, but hopefully someone can point me in the right direction.

[Lobstergirl, au gratin]

Jonathan, please put those plot details into your topic header. This helps the people searching for your book.

[Rainbowheart]

Key to the Treasure?

The Secret Hide-Out?

[Rainbowheart]

Still looking, Jonathan?