The man is addicted to morphine, and can think of nothing but death. Only morphine has made his life barely tolerable. He is in this fragile mental state because of the things that happened in the past; because of the things he was forced to encounter. During the First World War he ended up alone on an island - an island that was pure horror.
'Dagon' is a horror short story written by H. P. Lovecraft. It was first published in 1917.