I remember seeing the title for this episode before it aired, and I was eager with anticipation to see it, since the title was very intriguing leaving me wondering what it could possibly be about. For me, those kinds of titles work the best, directly referring to elements in the story, but at the same time keeping you from understanding its meaning until the end.
Although my review ranks this one very high, I have on occasion encountered fans who utterly disliked this one, and often rated it the worst of Series Four.
Doctor Who always works well when there's multiple mysteries to solve, and Roberts throws us right into the mix with the with the greatest mystery writer, Agatha Christie. The episode follows the "whodunit" format, allowing The Doctor to slowly work out what's going on, and keeping us attentive to hear his explanation.
Despite this episode almost mirroring a mix of Clue, Mrs. Marple, and various other novels from Christie, the reason for the likeness is explained within the story.
The setting of the episode, the pacing the mood, the characters and even the incidental music were all spot-on, which contributed to this episode's exceptional score.
Fans of the original series should recognize the actor portraying the Colonel as Henry Gordon Jago in "The Talons of Weng-Chiang."
In fact, the only drawback to this episode was the obvious gay relationship between Lady Edison's son and Davenport, one of the household staff. A minor drawback, and hardly worth mentioning.
Great dialogue through and through. Best episode Roberts had contributed.