A tricky story to discuss, because it actually hinges on a little bit of a twist that I'd rather not give away. The story features two periods in time, the first when he was a young boy and the second having grown up and visiting the house he grew up in. As a boy he was a little bit of an outcast, but there was a little girl he was good friends with. They would go out exploring the English countryside together, roaming as far as they could get away with. One day they discover a strange house, guarded by a very frightening dog. As they leave, the boy thinks he sees something which creeps him out, but he catches only a vague glimpse.
Soon thereafter, the boy becomes sick and spends many days in bed. After he recovers he learns that his friend has died, but nobody will tell him what happened. He grows up never having known what happened to her. He returns to his childhood home from the army with a fellow soldier along. They go out exploring and discover the strange house that he had found as a child.
And to reveal anymore would be to give too much away. This again is Aickman at his most mysterious, with a sense of the strange but providing no ability to really puzzle out what has happened.