The Lost Gardens by Anthony Eglin

I just finished reading this book. I had trouble putting it down. The suspense held on to the very end. A retired Doctor is hired by a young American girl who has inherited the Wickersham Estate in England from a stranger. She wants to restore the 10 acre gardens to reflect what they were in their heyday. 

It's learned that the land the estate stands on was once a priory, destroyed during the Reformation. But there was a secret maze of underground rooms that holds a secret and a healing fountain in an above ground chapel that holds the bones of an unknown male.

I can't wait to read his other books!