The Cavalier's Cup

Description for THE CAVALIER'S CUP by Carter Dickson:

SHADES OF DEATH

It had to be the specter of the long-dead Cavalier Sir Byng Rawdon who ghosted into the Oak Room at Telford Old Hall one night, spirited the bejeweled Cavalier's Cup from the locked safe...and left it standing on a table nearby.  The room's windows had been firmly latched, the heavy doors double-bolted from the inside---and a live witness had spent the entire night there and seen nothing!

ENTER SIR HENRY MERRIVALE

But the famous detective Sir Henry Merrivale wasn't spooked by ghost stories---in fact, impossible crimes always put him in high spirits.  A very live intruder was haunting the Hall, and it was up to the redoubtable Sir Henry to unmask the ubiquitous bugbear before his deviltries materialized into a more murderous form of mischief!

This is #22 in A Sir Henry Merrivale Mystery.