British manor murder

the long version

Although Perry, the earl of the house, and his sister, Poppy, are surprisingly accommodating to their jetlagged guests, Lucy feels uneasy after a fallen portrait sparks talk of a deadly family omen. The bad vibes come in quickly: snobby Aunt Millicent and her handmaiden Harrison unexpectedly drop by for the exhibition, and meals with the family are consistently tense. But real trouble begins when a body, bludgeoned by the chapel's gold-plated reliquary, is found in a hidden, sealed off room. Stranger still, the corpse is identified as Harrison's son, Cyril. From back cover.