Rent XTRO (1982)

Son, that alien's poisoned you against me - XTRO review by AM

This is the definition of a 'cult' film, despite it doing good business at the time of its release. Made by an eccentric, idiosyncratic director, it's an eccentric, idiosyncratic SF/horror unlike anything else at the time or perhaps since. It's not a ruthlessly efficient shocker in the manner of 'Alien', but instead a wildly perplexing and surprising film that has dropped off the radar and then reacquired a following on home video over years. 

A family is torn apart when the young son witnesses his father being abducted by a UFO, and three years later he appears to return to them. The emotional dynamics of a broken family are at the centre of the film, and particularly the boy, who is basically caught in a triangle between parents and the alien of the title. 

I'll avoid spoilers here and recommend you don't look up the best bits on YouTube (other tubes are available) because if you come to this film unspoiled it will be more fun. The production team apparently responded to an American backer's notes that the film needed to be 'off the wall' with a series of moments that deliver just that. There's also an atmosphere that is always at a tangent to standard horror storytelling. and a slightly homemade feeling that plays into its cult reputation. This includes the ending, which has been changed several times for theatrical and home video releases. The bluray gives you the chance to watch the film with all of them, and contributes to a feeling of the film being slightly unfinished or unresolved. There's also a 'director's version' for the disc, but this perhaps proves that archives should be left alone after a while, as it doesn't really improve significantly on the original.