Her husband, the handsome cad George Wickham, has had a disagreement with his friend, Captain Denny, that saw them fleeing into Pemberley's woodland, with gunshots ringing out.
Darcy and his guests mount a search party and in the woods they find Denny's bloodied body with a drunken Wickham kneeling beside it, proclaiming himself to blame for his friend's death. What follows is a painstaking account of the early 19th-century justice system, with Wickham standing trial for murder and threatening to stir up memories of old scandals, perhaps even destroying Darcy and Elizabeth's happiness in the process.
Often James' writing is constrained by the language of the period and by her commitment to mimic Austen's style but there are several moments of brilliance and flashes of the celebrated Austen wit.
Part of the problem with the plot is that we don't really care whether the odious Wickham is found guilty or not, nor do we ever believe he could shake the foundations of Darcy and Elizabeth's marriage. The other issue is one James herself addresses in her author's note - Austen deliberately steered clear of guilt and misery in her writing but a detective novel won't work without lashings of both.
Still, if they can get over their disapproval at sacrosanct literary ground getting such a trampling there is much for Jane-ites (as diehard Austen fans are known) to discover and enjoy.
The story has been seeded with references for them to spot - Sir Walter Elliot and his daughter Anne, from Persuasion, get a mention, for instance. And it is a joy to return to Pemberley and become re-acquainted with some of literature's most loved characters, even if there is something rather saccharine about both Elizabeth and Darcy these days.
So what would Austen have thought?
Well I imagine she would be as impressed as I am that at such a grand old age James' mind and writing remain razor sharp.