"Daleks in Manhattan" is a Doctor Who period piece, but one that doesn't just stick to the influence of the time in which it is set. New York in the 1930s was a place in which society looked both forward and backward at the same time, and this is reflected in the story's themes of grand gothic horror, social commentary, and glitzy show business.

It also contains callbacks to Doctor Who's own past and future, as we are about to discover.

Here are a few things that you should keep an eye out for, the next time you watch.

(The episode is available on iTunes and Amazon.)

Originally, this story was supposed to have been written by Steven Moffat, but he had to pull out due to other work commitments. This had a beneficial effect on Doctor Who in a couple of ways. First, the job went to Helen Raynor, the first woman to write a Dalek story for the TV show, and the first female script-writer in the modern era. Helen was working as script editor on the show, and had greatly impressed Russell T Davies with her script for the Torchwood episode "Ghost Machine". Secondly, Steven Moffat offered to write this season's "Doctor-lite" episode, which turned out to be "Blink", which is often voted as the best Doctor Who story ever.

Helen Raynor's inspirations for the script were the horror movies being made during the 1930s and early 1940s, such as Frankenstein (hence the large lightning conductor at the top of the Empire State Building), Island of Lost Souls (genetic experiments gone horribly wrong) and The Phantom of the Opera (the juxtaposition of show business glamor and terrifying creatures).

https://www.youtube.com/watch?v=lepJfSdvXQs

An early draft saw most of the action take place in Prohibition-era speakeasies , with hot jazz and Tallulah's boyfriend Laszlo being involved with the mafia. But Russell T Davies preferred the idea of a musical theater soundtrack—complete with Busby Berkeley dance number—so the action was split between Broadway and Hooverville.

This is not the first time the Daleks have been to the Empire State Building. Or rather it is chronologically, but not in the order the Doctor experiences things. While chasing the First Doctor, Vicki, Ian and Barbara in "The Chase", the Daleks land briefly on the observation deck in 1966.

https://www.youtube.com/watch?v=FPZXsIDBf5o

The character names are particularly good in this story. Solomon is of course named after the wise king in The Bible, even breaking a loaf of bread in half as a reference to 1 Kings 3:16-28, where King Solomon tests two women who both claim a baby as theirs by suggesting he be cut in two. Mr. Diagoras is named after the Greek poet Diagoras the Atheist, from the Fifth Century BC. Tallulah is, of course, named after the character of the same name from the 1976 movie Bugsy Malone.

Miranda Raison, who played Tallulah, has taken up quite a position within the Doctor Who universe, particularly in the Big Finish audio adventures. She appears as Lareen in "The Davros Mission", Tess Pilkelton and Myra Selfidges in "The Wreck of the Titan," the Shepherdess and Acquisitor Prime in "Persuasion," Margo and Xais in "The Romance of Crime," and the eighth incarnation of Drax in "The Trouble with Drax." She also appears as the Sixth Doctor's companion Constance Clarke in the "The End of the Line," a story in the series The Sixth Doctor: The Last Adventure.

There's a thrilling moment for Eleventh Doctor fans that wouldn't have been notable at the time. When the Doctor, Frank, Solomon and Martha are under attack from the Pigmen in the sewers, the Doctor, formulating a plan of action, says "Er, basically, run!"

There's a crossover between the Doctor Who and Star Wars universes in this story, in that Hugh Quarshie, who played Solomon, can also be seen as Captain Panaka in Star Wars: Episode I — The Phantom Menace. To British viewers, however, he is best known as Doctor Ric Griffin in the medical drama Holby City.

Deleted scenes include a moment where Tallulah finds a cage of the Daleks' failed genetic experiments, which had to be dropped as it was too expensive. Another plan was to kill off Laszlo, but this was felt to be too brutal.

Daleks have considered genetic experiments on humans before. In the Second Doctor story "The Evil of the Daleks", Daleks invade Victorian London, looking for the finest human they can, so they can extract "the human factor" from them and use it to make themselves stronger. Things take a turn for the personal when they decide that the most human human in the universe (and therefore prime candidate for their experiments) is Jamie McCrimmon, the Doctor's companion:

NEXT: 10 Things You May Not Know About ‘Evolution of the Daleks’

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