The following contains MAJOR SPOILERS for "The Unicorn And The Wasp," the seventh episode from the fourth season of BBC?s "Doctor Who."

Murder, mystery, aliens and a legendary author ... just the right ingredients for a 1920?s adventure.

As a period piece, ?The Unicorn and the Wasp? illustrates a romantic notion of the era and pits renowned crime writer Agatha Christie (Fenella Woolgar) against a bizarre and alien creature that resembles a giant wasp. ?What are you doing with that lead piping?? opens the episode with a Cluedo-style murder mystery that The Doctor (David Tennant) and Donna (Catherine Tate) will take charge of solving.

The real charm to the episode isn?t the giant wasp beast in human form but instead the ensemble that join this adventure in the country getaway. Each character brings with them an enigmatic an elusive backstory that they would rather keep concealed which adds an extra spark to the overall mystery. All of them have equal motive for killing Prof. Peach in the Library with the lead pipe.

Interspersed throughout the episode are some fantastic special effects, a lot of chin wagging and some genuine intrigue that captures the essence of Christie?s novels.

What Worked

The idea that The Doctor and Donna could drive across country and find Enid Blyton having tea with Noddy does prompt some interesting ideas on the origins of several childhood classics. But alas, the Time Lord admits the pint-sized character that drives along with Big Ears is nothing more than a work of pure fiction. Still, it would have been a fascinating adventure had Noddy indeed been real.

?The Unicorn And The Wasp? also included some brilliant laughs, mostly from The Doctor?s enthusiasm at taking on a mystery with Agatha Christie by his side. At every turn there was hilarity and bursts with the unexpected through random cries at Christie?s breakthroughs and squeals of excitement at the least little discovery. It was also great to see him again in awe of not just the human race but also the mercy of the Vespiform creature as it releases Christie from its influence in its final moments.

However, the most entertaining part (as is always the case in these stories) is the final summation. In this case it blended the normality of an Agatha Christie mystery with the outraging wildness of a ?Doctor Who? invasion. Taking each guest in turn, the investigative team successfully out his or her deepest and darkest secrets and expose them for who they are.

Even the world?s slowest car chase carried an element of excitement with Christie's life on the line and a killer wasp loose on planet Earth.

What Didn?t Work

The Doctor?s answer to stopping the cyanide poisoning was a little too convenient (although the run of charades in the kitchen did provide a string of laugh out loud moments). There was also the cartoon-like quality of the ?don?t make me angry? and zipping sounds during speech as Rev. Golightly (Tom Goodman-hill) becomes the wasp-like Vespiform.

Giving Credit Where Credit Is Due

"Doctor Who" stars David Tennant and Catherine Tate, and airs Saturday nights at 6.20 p.m. GMT on BBC 1, and then on Friday nights on The SciFi Channel at 8.30 p.m. ET. "The Unicorn And The Wasp" was written by Gareth Roberts and was directed by Graeme Harper.

Alan Stanley Blair is the assistant news editor for Airlock Alpha and its sister site Rabid Doll. Contributing from his home country of Scotland, he is currently studying for a diploma in freelance journalism and can be reached at anytime at ablair@airlockalpha.com.

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