Harry was a sympathetic ghost. Not like the poltergeist in number 33 - that one was a troublemaker.
Harry had been in the basement of number 21 Enfield Place for a few decades now. He had lost the ability to take account of time. He tried, for a while, after he had woken up to find himself dead. He had tried to record the passage of days and months, at first, by scratching lines in the soil of the cellar, just above where his body lay rotting, a few feet down. But he found it difficult to make the marks and the rats and other creatures ran over them, erasing them, or making other marks that confused him. In the end, he gave up.
It didn't really matter, he guessed, what time it was, or what day it was. It wasn't as if he had anything to do in a hurry.
He could see the passage of time was making its mark on his killer. Every now and then he would come down to the cellar, move a few boxes or take some away.
...
