Look to the Lady (Albert Campion Mysteries, Band 3)

Some objects just cry out to be stolen, and an obliging ring of international thieves stands ready to heed the cry. Their current target is the Gyrth Chalice, a priceless goblet that the Gyrth family has for centuries held in trust for the British Crown. Kept in a windowless chapel, and protected by a fearsome curse, the Chalice should be impervious to thievery. But the careless chatter about the Chalice of one of the family members seems to have called up all manner of misfortunes and the vague, bespectacled Albert Campion doesn't look like he'll be much help against them. But looks can be deceptive.