Light of Other Days by Bob Shaw (Analog, August 1966) begins with Garland and his pregnant wife, Selina, driving in the West of Scotland when they see a sign: “SLOW GLASS—Quality High, Prices Low”. Garland stops to inquire, much to the irritation of his wife (she is pregnant, neither of them are pleased about the matter, and it is causing significant friction between them).
After the couple go up the path to find the owner, they come to a cottage where they see the proprietor of the slow glass farm, Hagan, sitting on a wall. They also see, through the cottage window, a young woman holding a small boy. Hagan doesn’t invite the pair inside, but instead brings out a blanket so they can sit on the wall beside him.
Hagan then talks to them about the slow glass he has for sale—10 year in-phase material which has a view of the spectacular landscape in front of them, and which costs £200 for a four foot window. Garland is impressed by the 10 year specification, but the price is not as cheap as he hoped. Meanwhile, his wife Selina is shocked at the cost:
“You don’t understand, darling,” I said, already determined to buy.
“This glass will last ten years and it’s in phase.”
“Doesn’t that only mean it keeps time?”
Hagan smiled at her again, realizing he had no further necessity to bother with me. “Only, you say! Pardon me, Mrs. Garland, but you don’t seem to appreciate the miracle, the genuine honest-to-goodness miracle, of engineering precision needed to produce a piece of glass in phase. When I say the glass is ten years thick it means it takes light ten years to pass through it.”
When Hagan’s explanation about the time delaying properties of slow glass suddenly tails off, Garland looks away from the view he is buying and sees that Hagan is looking at the young woman and child, who have once again appeared in the window but seem to be paying no attention to what is going on outside.
After a few more clues are dropped (spoiler), the story resolves when Hagan goes to get a pane of slow glass for the couple. Selina takes the rug back into the cottage and—before Garland can stop her from going in—they discover the inside of the cottage is “damp, stinking, and utterly deserted”. There is no woman or child there, and the couple realise they have been looking at a pane of slow glass. When Hagan returns he sees what has happened and, before the couple go, tells them that his wife and child were killed by a hit and run driver on the Oban road. . . .
I think that this story would be better without its final line (“He was looking at the house, but I was unable to tell if there was anyone at the window”) but this is a very minor quibble about what is an excellent piece, a deserved classic, and something that should have been that year’s Hugo & Nebula winner (it lost against Larry Niven’s Neutron Star in the Hugo ballot, and Richard Wilson’s The Secret Place in the Nebula one).
***** (Excellent). 3,150 words. Story link.
1. The rest of the stories in the “Slow Glass” series are listed at ISFDB.