Cornwall, 1910. On a remote tidal island, the Viscount of Tithe Hall is absorbed in feverish preparations for the apocalypse that he believes will accompany the passing of Halley's Comet. The Hall must be sealed from top to bottom - every window, chimney and keyhole closed off before night falls. But what the pompous, dishonest Viscount has failed to take into account is the danger that lies within... By morning, he will be dead in his sealed study, murdered by his own ancestral crossbow.

All eyes turn to Stephen Pike, Tithe Hall's newest under-butler. Fresh out of Borstal for a crime he didn't commit, he is the wrong man in the wrong place at the wrong time. His unlikely ally? Miss Decima Stockingham, the foul-mouthed, sharp as a tack, 80-year-old family matriarch. Fearless and unconventional, she relishes chaos and puzzles alike, and a murder is just the thrill she's been waiting for.

Together, this mismatched duo must navigate secret passages, buried grudges and rising terror to unmask the killer before it's too late...