"Mr. McCaslin" by Peter S. Beagle

Three childhood friends in the Bronx encounter a remarkable manifestation of death and embark on an unforgettable adventure. The author reflects on childhood memories in New York City, focusing on extreme summers and frequent funerals. Mr. McCaslin reveals he knows he is dying, and they discuss keeping a dark terrier away. A lost dog leads to a desperate rescue attempt, and they reflect on Mr. McCaslin's letter and the supernatural.