Change the word "read" to the word "sail", changing only one letter each time to make a new word. Try to achieve this in no more than six stages.

read, raad, raid, rail, sail

read, road, roid, roil, soil, sail

read, rend, send, sand, said, sail

Explanation:

i wrote a computer program to do so using the dictionary and that's how I found out about the word raad, which apparently means "a legislative assembly in one of the Boer republics of South Africa before the establishment of British administration" as per Merriam-Webster.

The word raad could easily be replaced by Reid if names are allowed.

I'll get back here if I find solutions with more stages but more "normal" words.

Update - roid as in steroid is a slang word, but seems somewhat acceptable to me.

Update 2 - the third example only uses "normal" words.

a.) it provides a clue to solve the mystery.