The Avengers is a British spy-fi series that first aired in 1961, and ended in 1969. The show was initially more crime-based, and focused on Dr. David Keel (Ian Hendry) and John Steed (Patrick Macnee) solving crimes, while also avenging the death of Keel's fiancée. However, after only one season, Hendry left the show, making John Steed its main character. As the show progressed, it became more and more fantastical, with various science fiction-oriented plots.
Like many British shows of its time, The Avengers has missing episodes. The show was shot on 405-line videotape using a multicamera setup, resulting in episodes being wiped for reuse. Only three episodes survive in full via telerecordings, while the first act of the very first episode also survives. Only episodes from Season 1 are missing; every other episode remains intact.