Doctor Who-The Unicorn And The Wasp

                          The doctor and Donna land in England in 1926 at a party hosted by the Lady  Eddison and her husband Colonel Hugh. During the introductions they are introduced to the guest of honor: Mrs. Agatha Christie herself. This is timely since the area is being menaced by a theif known as the Unicorn. When the doctor takes a look at the newspaper amid all these introductions,he notices the date is the same one where Christie disappears and is found ten days later at a far off motel with amnesia of this very day itself. One of a the guests,a professor Peach is soon found dead. The corpse leaves behind a viscous substance the doctor instantly recognizes as morphic residue. After a stone sculpture lands on and kills the servant Miss Chadrakala she makes a reference to a mysterious lost child. Agatha Christie and the doctor pair up to interview everyone at the party as to their whereabouts at the time of the murders while Donna does some investigating of her own. She locates the bedroom where the Butler Greeves tells her Lady Eddison laid ill 40 years earlier after a Maleria outbreak upon a return from India,that had been thereafter abandoned. Alone in the room Donna is set upon by a giant wasp she narrowly escapes,which leaves its enormous stinger in the wall.
Upon calling the doctor in to investigate further the doctor locates the same morphic residue on the stinger as found on the cadaver of Professor Peach. When they regroup with the dinner guests in the study,the doctor is poisoned by cyanide and instructs Donna to concoct a series of different ingredients to expel the poison from his body.  

          This inspires the doctor to add pepper,containing the insecticide piperine, to their food in order to repel the wasp,an alien Vespiform according to the doctor. After gathering the guests later,he learns that one of them is actually the Unicorn posing as a dinner guest. But more importantly,through Agatha's investigation that in India the younger Lady Eddison had become impregnated by a Vespiform taking human form-not only the cause of her Malaria but also that the valuable Firestone pendant she is wearing is a conduit for its powers. Deducing from his age and his adoption,the doctor deduces the other guest the Reverand Golightly is Eddison's illegitimate son with the alien Vespitform. He reverts to his natural form and,realizing that she is partly responsible for what has happened with Eddison reading Agatha's books before this encounter and the Firestone is a telepathic enhancer connecting her with Golightly,she pursues him in her car with Donna and the doctor following. Donna throws the Firestone into the river when the memories are reversed from Agatha to the the Vespiform and it sinks in the river,as Agatha's memories of her encounter with the doctor and Donna are erased. Upon leaving on their mission,the doctor shows Donna an Agatha Christie novel found millennia in Earth's future about their encounter-indicating her memories were not so fragile after all.

               This is a wonderfully executed comic mystery type setup that matches what might've otherwise been a 1920's era historical murder mystery send up on the line of 1982's Black Orchid into something quite a bit more compelling. Agatha Christie is depicted here as a hard working writer who hasn't valued her work much until the doctor inspires her to follow her own instincts in helping to solve the mystery developing around her. Still even she isn't prepared for the involvement of what essentially amount up to gigantic alien wasps. The characters are all highly colorful. Most humorous is during the interview process after the murder of the professor, each one of them remembers the question asked with a very thinly veiled disguised of their many hidden agendas: including pornographic literature,a homosexual affair and the identity of the Unicorn thief herself.  This is also the story where Donna actually kisses the doctor,of course within the story only the shock needed to effectively dispose of the cyanide that he was poisoned with. In the end this is an excellent murder mystery story,very much playing out like an Agatha Christie story such as Miss Marple with a science fiction twist.