NPR Sunday Puzzle (Oct 2) - Four-letter O-word

NPR Sunday Puzzle (Oct 2) - Four-letter O-word

Q: Think of a four-letter word starting with O. Change one of its letters to a new letter and rearrange to get a new four-letter word that's a synonym of the first. Then change one of its letters to a new letter and rearrange to get a third four-letter word that's a synonym of the first two. What words are these?

I think there is only one answer that fits the clues of this puzzle... but I'm not going to give you the answer until after the deadline.
Edit: Yes, I believe there is ONLY one answer that fits the clues...

ONLY --> LONE --> SOLE