The trailer for the 50th anniversary special edition of the BBC's Dr Who made its debut on UK television on Saturday night, sparking a feverish hunt for clues among the programme's global legion of fans.
The world's longest running science fiction series will return on 23 November for a 75-minute one-off adventure entitled The Day of the Doctor. For the first time, the programme will be transmitted simultaneously all around the world, in as many as 200 countries, guaranteeing record viewing figures for a single edition of the programme.
The show will also go on limited theatrical release in 3D in the United States, while in the UK it will be broadcast in both 3D and 2D. A 3D Blu-ray of the programme will be released 10 days after transmission in the UK.
The trailer itself is a tribute to the show's long history, and to the 11 actors who have so far played the titular character on television. Mixed in with the images of the 11 Doctors are a selection of baddies and props from the show's five decades, including Cybermen, Weeping Angels and - of course - the Daleks.
The next actor to play Dr Who will be Peter Capaldi, who will grab the key to the Tardis from Matt Smith later this year.
The first episode of Dr Who, starring veteran actor William Hartnell as the Doctor, was filmed live and almost postponed, following the assassination of US President John F Kennedy 24 hours earlier.
The programme went on to establish a unique place in the UK's television affections, until falling audiences and dwindling budgets led to its suspension in 1989.
Demands from audiences for more sophisticated special effects in the wake of films such as Star Wars led to a one-off transatlatic co-production in 1996, starring Paul McGann as the Doctor, but no series materialised until Russell T Davies revived it successfully in 2005, with Christopher Eccleston as an energetic northern Doctor.
The trailer contains cryptic references to all this history, including a fob watch, several sonic screwdrivers and K-9 (the Doctor's robot dog). There's the number 17162311, a reference to the time and date of the first broadcast, a lingering look at assistant Sarah Jane (the late Elisabeth Sladen), and just a glimpse of some clockwork droids.
The soundtrack, meanwhile, morphs pleasingly from the early BBC Radiophonic Workshop version of the theme tune, to the modern, brassy, orchestral one.
Watch the new trailer for the 50th anniversary Dr Who special on YouTube, below: