It's almost Christmas in the small English village of Finch—and everyone is sick. Although many of the villagers regretfully decline their invitations to Emma and Derek Harris's annual Christmas bash, Lori Shepherd has no intention of missing it. When the winter weather takes a turn for the worse, it's agreed that none of the guests will leave until morning. There's general merriment as the Christmas party becomes a pajama party—until a car appears in the winding driveway and promptly slides off the slick pavement and into a tree.

Matilda Tilly Trout—a lost and scatterbrained middle-aged woman—is mercifully unhurt and invited to stay the night. The next morning, Emma asks her guests if they would like a tour of the Manor—including a secret room she recently discovered. Several guests put forth guesses as to its purpose, but it's Tilly who correctly identifies the room as a chapel. Placing a palm on one of the ornately carved panels, Tilly finds a hidden compartment concealing a pile of glittering treasure—including an exquisitely decorated heart made of solid gold. Where did it come from, and why does it look so different from everything else in the chapel? Why didn't Emma even know about this hidden compartment in her own home until now—and how did Tilly?