The Testament of Arkadia. Season 1, Episode 23. First broadcast Thursday 12 February 1976. Stranded in a cold and purposeless corner of an indifferent universe, adjacent to the end of everything, the crew of Moonbase Alpha make a discovery which changes the meaning not just of their journey but of their very existence, and which drives this week’s Large Hot Italian Guest Star and his posh new girlfriend to make an irrevocable decision.

The Troubled Spirit. Season 1, Episode 22. First broadcast Thursday 5 February 1976. The 70s have come roaring back on Moonbase Alpha this week — with a séance, some dank hydroponic weed, and a beardo hippy and his Coral Electric Sitar. All of which inevitably summons an irrational paranormal phenomenon intent (as always) on killing everyone on the base. But not before some urgent and profound philosophical questions are raised, including Why?, What on earth is going on here? and Death, eh? What’s with that?

Space Brain. Season 1, Episode 21. First broadcast Thursday 29 January 1976. This month, executive interference turns a simple tale of mutual trust in a universe full of life and purpose into a bleak story about shooting a benevolent but defenceless cosmic intelligence through the brain. Still, we did enjoy the foam party on the way.

Missing Link. Season 1, Episode 20. First broadcast Thursday 22 January 1976. This month, John Koenig awakens on an island full of noises, sounds and sweet airs: there he meets Temu Prospero and his daughter Vana, who is curious about this human concept you call love. Meanwhile, back on the base, Helena, Victor and Paul decide that killing the Commander would significantly improve everyone’s mood.

Ring Around the Moon. Season 1, Episode 19. First broadcast Thursday 15 January 1976. This month, the people of the mythical planet Triton are so (understandably) keen to avoid any contact with the human race that they send a large yellow lightbulb to capture the Moon and to issue urgent demands for the entire contents of the base’s OneDrive. These demands mostly involve abducting Helena and inserting things into her brain, giving Barbara the chance to try out a bewildering array of new facial expressions.

The Infernal Machine. Season 1, Episode 18. First broadcast Thursday 8 January 1976. This month, Leo McKern turns up on the Moon with his enormous scary spaceship husband, who threatens to kill everyone on the base and decimate its sizeable collection of Kenner die-cast model vehicles. But there’s also a moving depiction of grief here, and some kind of attempt to explore why exactly we all continue putting up with each other.

The Last Sunset. Season 1, Episode 17. First broadcast Thursday 1 January 1976. This month’s mysterious immortal beings are — as usual — keen to avoid meeting the crew of Moonbase Alpha, but instead of simply killing everyone on the base, they decide to give them everything they ever wanted. Inevitably, things turn out very badly.

Another Time, Another Place. Season 1, Episode 16. First broadcast Thursday 18 December 1975. This month, an unexpected scripting anomaly returns the Moon to Earth’s orbit, where it will inevitably crash into another slightly older Moon, killing everyone on the base. But in the meantime, we experience a strange and elegiac meditation on having nowhere to belong and on our subjection to the vagaries of time. Haunting and inexplicable.

The Full Circle. Season 1, Episode 15. First broadcast Thursday 11 December 1975. This month, a picnic on a verdant new planet — fresh air, space buggies, aggressive and bloodthirsty lice, hitting people with rocks, and menacing people with burning knives. But, for once, no one wants to kill everyone on the base, except the audience, probably.

Earthbound. Season 1, Episode 14. First broadcast Thursday 4 December 1975. This month, to our surprise, Christopher Lee turns up on Alpha, not to kill everyone on the base for once, but just to be terribly nice to everyone. But Alpha harbours a villain of its own, one even deadlier than Christopher Lee, but mostly to himself.