UK4 - When a Star Falls (another one in which Graeme Morris had an involvement).
I 1st bought it in 1987, and am only now running it for a group for the 1st time.
From a fantastic opening sequence (I copied all the memories to slips of paper and hurled them into the players' faces when the Memory Web died), to neatly designed encounter locations, stir in a liberal dose of roleplaying, and tie it together with the most interesting plot I've ever seen in a published adventure.
And it never appears on any of the 'best of' lists either. I guess the UK made adventures just didn't have the impact they should have done in the States - shame, as many of them were better than most of the stuff the US writers were churning out.