SOLVED. YA or boys book where protagonist was left a clue to relative's treasure. [s]

[Ben]

The protagonist was left a clue in a family members will to some treasure. I think it was his uncle but could have been more distant although I'm fairly certain the clue was a key and note and the treasure wasn't gold. I remember one part when the boy is in a telephone box talking to someone while the wire was cut. I think they were after the treasure too and it was somewhat of a mystery/adventure story in a small town. Towards the end of the book the boy uncovers some secret in his relative's house, I seem to remember him unlocking a small hidden tunnel but this key was a point of tention throughout the book. I read it around five years ago, it came from an English high school library and is set in the modern day but I can't say where for certain.

[Kris]

A guess - Mortom by Erik Therme?

Google search - site:www.goodreads.com "young adult" "a clue" "treasure" "key" "a note" mystery town

[Ben]

Yes this is the one thank you!

[Kris]

You're welcome, Ben. Glad you found your book. It's good to guess in this group.