Secret of Benjamin Square, The (Vintage Paperback) by Jennifer Plum

The deadly trove...

The house in the London suburb was three stories high and as solid looking as the Great Pyramid of Egypt. Hundreds of years old, it showed the strength of its age, and Nancy Hooker could not help feeling intimidated by her first sight of her new home. An American, she was here with her brother, Robert, to accept an astonishing legacy that made him the eleventh Baron Benjamin. But the legacy required that they live in this house...and the house was fabled for hundreds of years as the hiding place of a fabulous royal treasure.

Scarcely had Nancy and Robert arrived before it seemed that someone wanted to drive them away! Were the intruders in the manor seeking the ancient treasure...or were they there to destroy the last of the Benjamins?