The first live-action series Gerry Anderson made after his 60's Supermarionation successes, UFO is something of an underrated gem, but also a genuine oddity.
Rather optimistically set in 1980, UFO's hardware was pure THUNDERBIRDS - tanks, submarines, spaceships, skydiving planes, a top secret moonbase and underground headquarters disguised as a film studio, but the series' subject matter was surprisingly downbeat. The heroes of UFO were a set of grim-faced, square-jawed chaps working for SHADO, an organisation dedicated to battling alien invaders who came to Earth to steal our internal organs for their own nefarious purposes. SHADO were forced to work entirely in secret to avoid worldwide panic, thus their ongoing struggle against the aliens - about whom nothing was revealed aside from their penchant for plundering our innards - always had a very ambivalent Cold War atmosphere to it.
ITV never really knew how to handle UFO and scheduled it haphazardly around the various regions. Presumably because of this, plans for a second series were shelved and instead metamorphised into SPACE: 1999. Whereas SPACE: 1999 traded in cod philosophy, UFO went for a bizarre fusion of soap opera realism - one episode deals with the broken marriage of one of the main characters with the relationship collapsing because of the secret nature of the SHADO organisation - and PRISONER-like surrealism and psychedelia, with another episode featuring a sepia-lensed full-blown acid trip. No wonder the ITV schedulers of the early 1970's hadn't a clue what to do with the show.